HAVANA -- Cuba's admission that it was secretly sending aging weapons systems to North Korea has turned the global spotlight on a little-known link in a secretive network of rusting freighters and charter jets that moves weapons to and from North Korea despite U.N. sanctions.

The revelation that Cuba was shipping the arms, purportedly to be repaired and returned, is certain to jeopardize slowly warming ties between the U.S. and Havana, although the extent of the damage remains uncertain. Experts said Cuba's participation in the clandestine arms network was a puzzling move that promised little military payoff for the risk of incurring U.N. penalties and imperiling detente with Washington.

The aging armaments, including radar system parts, missiles, and even two jet fighters, were discovered Monday buried beneath thousands of tons of raw Cuban brown sugar piled onto a North Korean freighter that was seized by Panama as it headed for home through the Panama Canal.

North Korea is barred by the U.N. from buying or selling arms, missiles or components, but for years U.N. and independent arms monitors have discovered North Korean weaponry headed to Iran, Syria and a host of nations in Africa and Asia. The U.N. says North Korea also has repeatedly tried to import banned arms. What's more, analysts say, it maintains a thriving sideline in repairing aging Warsaw Pact gear, often in exchange for badly needed commodities, such as Burmese rice.

"They don't know how to grow rice, but they know how to repair radars," said Daryl Kimball, executive director of the Arms Control Association, a private group dedicated to promoting arms control.

"The North Koreans are taking desperate measures to pursue that work. Despite the best efforts of the international community to cut off arms transfers to and from North Korea, it will continue in some form."

The surprise for many observers was that the latest shipment of arms headed to North Korea comes from Cuba, which acknowledged late Tuesday that it was shipping two anti-aircraft missile systems, nine missiles, two Mig-21 fighter jets and 15 jet engine, saying they were headed to North Korea to be repaired there.

The discovery aboard the freighter Chong Chon Gang was expected to trigger an investigation by the U.N. Security Council committee that monitors the sanctions against North Korea, and Panamanian officials said U.N. investigators were expected in Panama on Thursday. Britain's U.N. Ambassador, Mark Lyall Grant, said that "any weapons transfers, for whatever reason, to North Korea would be a violation of the sanctions regime."

If Cuba wanted to send the weapons for repairs and have them returned, it would have needed to get a waiver from the Security Council committee monitoring the North Korea sanctions. A spokesman for Luxembourg's U.N. Mission, which chairs the North Korea sanctions committee, told The Associated Press that there had been no such request from Cuba.

Democrat Robert Menendez, the Cuban-American chairman of the Senate Foreign Relations Committee, said the incident "almost certainly violated" U.N. sanctions and urged the Obama administration to bring it to the Security Council for review.

"Weapons transfers from one communist regime to another hidden under sacks of sugar are not accidental occurrences," Menendez said Wednesday, adding that it "reinforces the necessity that Cuba remain on the State Department's list of countries that sponsor state terrorism."

Panama's seizure of the freighter, which saw its North Korean captain try to commit suicide and 35 crewmen arrested after resisting police efforts to intercept the ship in Panamanian waters, was badly timed for officials working on baby steps toward a limited detente between the U.S. and Cuba.

High-ranking Cubans were in Washington on Wednesday for migration talks that are supposed to be held every six months but have been on ice since January 2011, as the nations remain at odds on issues like Cuba's imprisonment of U.S. government subcontractor Alan Gross.

"I don't think you can sugarcoat this," said Ted Piccone, senior fellow and deputy director for foreign policy at the Washington-based Brookings Institution. "You have a suspicious cargo of weapons going to a heavily sanctioned state, and this is bad for U.S.-Cuba relations. The timing, the same week as the restart of long postponed migration talks, couldn't be worse."

In the past those discussions have provided a rare opportunity to discuss other issues informally in one of the few open channels of dialogue between the countries.

U.S. and Cuban representatives last month also sat down for talks on resuming direct mail service. Earlier this year, a U.S. judge allowed a convicted Cuban intelligence agent to return to the island rather than complete his parole in the United States. And there have been whispers that Washington could remove Cuba from its annual list of state sponsors of terrorism.

On Tuesday, Rep. Ileana Ros-Lehtinen, a Florida Republican, urged a suspension of the migration talks.

"At a minimum this development will decrease the chances of any change in U.S. policy," Piccone said. "Or at least postpone changes that have been discussed quietly and publicly for some time in Washington."

State Department deputy spokeswoman Marie Harf said Wednesday that Washington had told Cuban officials that it would discuss the seized ship with them soon, but that it would not be a focus of the one-day migration talks.

Panamanian officials said Wednesday that the ship's crew was the subject of a criminal investigation that could lead to charges, adding that two North Korean diplomats based in Havana had been issued visas to travel to Panama to talk with authorities about the case. Panamanian authorities said it might take a week to search the ship, since so far they have only examined two of its five container sections.

North Korea's Foreign Ministry said Wednesday that Panama should release the crew because no drugs or illegal cargo were aboard, reiterating Cuba's explanation that, "this cargo is nothing but aging weapons which are to be sent back to Cuba after overhauling them according to a legitimate contract."

Experts said the equipment found aboard the North Korean vessel does not pose a military threat to the United States or its allies.

Like other aspects of Cuba's economy and infrastructure since the collapse of the Soviet Union, the island's armed forces rely greatly on aging technology that requires frequent maintenance and parts that are difficult to obtain.

North Korea has a robust capability to repair and upgrade such Soviet-era military equipment, and a track record of doing that in exchange for commodities such as sugar. Soviet-built air-defense missiles, radar systems and MiG-21 fighter jets are complex enough to periodically require a factory repair in addition to regular maintenance.

North Korea is also known to be seeking to evade sanctions and get spare parts for its own weapons systems, particularly Mig jet fighters. That raises the possibility that in lieu of cash, Cuba was paying for the repairs with a mix of sugar and jet equipment, experts said.

"We think it is credible that they could be sending some of these systems for repair and upgrade work," said Neil Ashdown, an analyst for IHS Jane's Intelligence. "But equally there is stuff in that shipment that could be used in North Korea and not be going back."

"Upgrading, servicing and repairing, that's what the North Koreans do," added Hugh Griffiths, arms trafficking expert at the Stockholm International Peace Research Institute. "It is military equipment prohibited under U.N. sanctions, so whether payment is made in the form of barter trade or foreign currency, it still constitutes a violation."

The private defense analysis group IHS said satellite tracking data showed that another North Korean vessel had made a similar trip last year, crossing the Panama Canal on its way to Cuba, then crossing back, although there was no evidence yet that it had been carrying arms.

Griffiths also said his institute earlier this year reported to the U.N. a discovery it made of a flight from Cuba to North Korea that traveled via central Africa, a flight it said should now be receiving new scrutiny.

Under current sanctions, all U.N. member states are prohibited from directly or indirectly supplying, selling or transferring arms, missiles or missile systems and the equipment and technology to make them to North Korea, with the exception of small arms and light weapons.

The most recent resolution, approved in March after Pyongyang's latest nuclear test, authorizes all countries to inspect cargo inside or transiting through their territory that originated in North Korea. It also lets countries inspect cargo destined for North Korea if a state has credible information the cargo could violate Security Council resolutions.

____

Weissenstein reported from Mexico City. Edith M. Lederer at the United Nations, Malin Rising in Stockholm, Foster Klug in Seoul, South Korea, Vladimir Isachenkov in Moscow and Juan Zamorano in Panama contributed to this report

____

Follow Michael Weissenstein on Twitter at http://twitter.com/mweissenstein

Follow Peter Orsi on Twitter at http://twitter.com/Peter_Orsi

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Captions courtesy AP.
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  • January 1951

    Six months after invading North Korean forces started the Korean War, North Korean leader and founder Kim Il Sung says in a speech that U.S. and South Korean forces were the actual invaders and had prompted his army to retaliate. Kim vows to annihilate the North's enemies. <em>Caption: In this March 7, 2013 photo released by the Korean Central News Agency (KCNA) and distributed March 8, 2013 by the Korea News Service, North Korean leader Kim Jong Un, center, uses binoculars to look at the South's territory from an observation post at the military unit on Jangjae islet, located in the southernmost part of the southwestern sector of North Korea's border with South Korea. (AP Photo/KCNA via KNS) </em>

  • January 1952

    Kim Il Sung likens U.S. forces to Nazis and says that the war is turning into a mass grave for U.S. forces. <em>Caption: In this March 7, 2013 photo released by the Korean Central News Agency (KCNA) and distributed March 8, 2013 by the Korea News Service, North Korean leader Kim Jong Un, center, walks with military personnel as he arrives for a military unit on Mu Islet, located in the southernmost part of the southwestern sector of North Korea's border with South Korea. (AP Photo/KCNA via KNS)</em>

  • May 1972

    Kim Il Sung tells Harrison Salisbury and John Lee of The New York Times that because of perceived U.S. hostility, "we are always making preparations for war. We do not conceal this matter." <em>Caption: North Koreans attend a rally in support of a statement given on Tuesday by a spokesman for the Supreme Command of the Korean People's Army vowing to cancel the 1953 cease-fire that ended the Korean War as well as boasting of the North's ownership of "lighter and smaller nukes" and its ability to execute "surgical strikes" meant to unify the divided Korean Peninsula, at Kim Il Sung Square in Pyongyang, North Korea, on Thursday, March 7, 2013. (AP Photo/Jon Chol Jin)</em>

  • March 1993

    North Korea declares a "semi-state of war" to protest joint U.S.-South Korean war games that it says threaten its security. Amid a standoff with Washington over its nuclear program, it also threatens to withdraw from the Nuclear Non-Proliferation Treaty. <em>Caption: In this Dec. 12, 2012 file photo released by Korean Central News Agency, North Korea's Unha-3 rocket lifts off from the Sohae launch pad in Tongchang-ri, North Korea. (AP Photo/KCNA, File)</em>

  • 1994

    In an appearance of what will become a well-worn phrase, a North Korean negotiator threatens to turn Seoul into "a sea of fire." Fearing war, South Koreans clear store shelves of instant noodles, water, gas and other necessities. <em>Caption: Female North Korean traffic police officers gather in front of bronze statues of the late leaders Kim Il Sung and Kim Jong Il to pay their respects in Pyongyang, North Korea on Saturday, Feb. 16, 2013. (AP Photo/David Guttenfelder)</em>

  • September 1996

    North Korea threatens "hundredfold and thousandfold retaliation" against South Korean troops who had captured or killed armed North Korean agents who had used a submarine to sneak into the South. <em>Caption: North Korean soldiers gather along a Pyongyang street during heavy snowfall on Sunday, Feb. 17, 2013. (AP Photo/David Guttenfelder)</em>

  • September 1996

    North Korea threatens "hundredfold and thousandfold retaliation" against South Korean troops who had captured or killed armed North Korean agents who had used a submarine to sneak into the South. <em>Caption: A North Korean soldier smokes a cigarette as snow falls in Pyongyang on Sunday, Feb. 17, 2013. (AP Photo/David Guttenfelder)</em>

  • January 2002

    After President George W. Bush labels North Korea part of an "axis of evil" with Iraq and Iran, Pyongyang calls the remark "little short of a declaration of war." North Korea's Foreign Ministry warns it "will never tolerate the U.S. reckless attempt to stifle the (North) by force of arms but mercilessly wipe out the aggressors." <em>Caption: A North Korean portrait photographer instructs North Korean soldiers to pose for a picture under a mosaic of the late leaders Kim Il Sung and Kim Jong Il at an exhibition in Pyongyang on Sunday, Feb. 17, 2013 where Kimjongilia flowers, named after Kim Jong Il, were on display. (AP Photo/David Guttenfelder)</em>

  • January 2010

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  • May 2010

    After a Seoul-led international investigation blames a North Korean torpedo for the sinking of a South Korea warship that killed 46 sailors, Pyongyang issues a denial and warns of a "prompt physical strike." In November 2010, the North attacked a front-line island, killing four South Koreans. <em>Caption: North Koreans cross a railroad bridge over a riverbed south of Mount Myohyang, and north of the capital city of Pyongyang, North Korea, Saturday, Feb. 23, 2013. (AP Photo/David Guttenfelder)</em>

  • November 2011

    A day after South Korea conducts large-scale military drills near the island hit by the North in 2010, the North's Korean People's Army threatens to turn Seoul's presidential palace into a "sea of fire." <em>Caption: In this Feb. 16, 2013 image made from video, North Korean leader Kim Jong Un, center, waves as he attends a statue unveiling ceremony at Mangyongdae Revolutionary School in Pyongyang, North Korea on the anniversary of late North Korean leader Kim Jong Il's birthday. (AP Photo/KRT via AP Video)</em>

  • April 2012

    North Korea holds a massive rally denouncing conservative South Korean President Lee Myung-bak as a "rat." It says he should be struck with a "retaliatory bolt of lightning" because of his confrontational approach toward Pyongyang. <em>Caption: Rows of North Korean children stand and salute at a sports arena in Pyongyang for a national meeting of the Children's Union on Saturday, Feb. 16, 2013. (AP Photo/Jon Chol Jin)</em>

  • June 2012

    North Korea's military warns that troops have aimed artillery at seven South Korean media groups to express outrage over criticism in Seoul of ongoing children's festivals in Pyongyang. It threatens a "merciless sacred war." <em>Caption: South Korean army soldiers patrol along the barbed-wire fence near the border village of Panmunjom, which has separated the two Koreas since the Korean War, in Paju, north of Seoul, South Korea, Saturday, Feb. 16, 2013. (AP Photo/Lee Jin-man)</em>

  • October 2012

    An unidentified spokesman at the powerful National Defense Commission warns that the U.S. mainland is within range of its missiles and says Washington's recent agreement to let Seoul possess missiles capable of hitting all of North Korea shows the allies are plotting to invade the North. <em>Caption: North Korean soldiers and others gather in front of bronze statues of the late leaders Kim Il Sung and Kim Jong Il to pay their respects in Pyongyang, North Korea on Saturday, Feb. 16, 2013. (AP Photo/David Guttenfelder)</em>

  • North Korean soldiers lay flowers at the base of bronze statues of the late leaders Kim Il Sung and Kim Jong Il to pay their respects in Pyongyang, North Korea on Saturday, Feb. 16, 2013. North Koreans turned out to commemorate what would have been the 71th birthday of Kim Jong Il who died on Dec. 17, 2011. (AP Photo/David Guttenfelder)