BELFAST, Northern Ireland -- Secretary of State Hillary Rodham Clinton said Friday that the United States and Russia are committed to trying again to get President Bashar Assad's regime and the rebel opposition to talk about a political transition in Syria, setting aside a year and a half of U.S.-Russian disagreements that have paralyzed the international community.

Clinton stressed, however, that the U.S. would insist once again that Assad's departure be a key part of that transition, a position not shared by the Russians.

In her first comments on the surprise three-way diplomatic talks held Thursday with Russian Foreign Minister Sergey Lavrov and U.N. peace envoy Lakhdar Brahimi, Clinton said Washington and Moscow agreed to support a new mediation effort Brahimi would lead. She called Thursday's discussions "constructive," while adding that much work remained and suggesting that neither side shifted its fundamental position.

"We reviewed the very dangerous developments inside Syria," Clinton said in Northern Ireland. "And both Minister Lavrov and I committed to supporting a new push by Brahimi and his team to work with all the stakeholders in Syria to begin a political transition."

"It was an important meeting, but just the beginning," she added. "I don't think anyone believes there was some great breakthrough. No one should have any illusions about how hard this remains, but all of us with any influence on the process, with any influence on the regime or the opposition, need to be engaged."

Neither Assad nor any opposition group has agreed to a cease-fire and talks. Both sides believe they can resolve the conflict militarily. Even if the U.S. and Russia reach a broader agreement on a path forward, bringing most of the world with them, it is unclear if that will have any effect on the fighting in Syria.

The 40-minute meeting with Lavrov and Brahimi immediately seemed to ease some of the tensions between the U.S. and Russia over how best to address Syria's bloody, 21-month civil war. Through much of the conflict, the former Cold War foes have argued bitterly. The U.S. has criticized Russia for shielding its closest Arab ally. Moscow has accused Washington of meddling by demanding Assad's downfall.

Clinton said nothing that suggested either government had changed its position, and Lavrov made no public comments after the meeting. But with rebels fighting government forces on the outskirts of Syria's capital and Western governments warning about possible chemical weapons deployment by the Assad regime, Clinton emphasized the importance of taking another shot at a peaceful transition deal.

Diplomatic efforts are needed to gauge "what is possible in face of the advancing developments on the ground which are increasingly dangerous not only to Syrians, but to their neighbors," Clinton said, in an apparent reference to Syria's chemical weapons arsenal, which has become the focus of Western nervousness about the civil war.

Brahimi said after the talks that he would put together a peace process based on a political transition strategy the U.S. and Russia agreed on in Geneva in June. At that time, the process quickly became bogged down over how the international community might enforce its conditions.

But instead of addressing the plan's shortcomings, Clinton stressed its continued value, saying it would commit any future Syrian authority to democratic principles and international human rights standards.

Clinton also said the strategy would have to mean the end of the four-decade Assad regime – a contentious point with Moscow, which has insisted that Syria's leadership is not for the United States or any other outside party to decide on.

"The United States stands with the Syrian people in insisting that any transition process result in a unified, democratic Syria in which all citizens are represented – Sunni, Alawi, Christians, Kurds, Druze, men, women. Every Syrian must be included," Clinton told reporters. "And a future of this kind cannot possibly include Assad."

The plan Brahimi is hoping to resuscitate was crafted earlier this year by his predecessor as the Syria peace envoy, former U.N. Secretary-General Kofi Annan. Annan's plan never got off the ground, and he resigned his post in frustration.

It starts with several demands on the Assad regime to de-escalate tensions and end the violence that activists say has killed more than 40,000 people since March 2011. It then requires Syria's opposition and the regime to put forward candidates for a transitional government, with each side having the right to veto nominees proposed by the other.

If anything resembling Annan's plan takes hold, it would surely mean the end of Assad's presidency. The opposition has demanded his departure and has rejected any talk of him staying in power. Yet it also would grant regime representatives the opportunity to block Sunni extremists and others in the opposition that they reject.

The United States blamed the collapse of the process last summer on Russia for vetoing a third resolution at the U.N. Security Council that would have applied world sanctions against Assad's government for failing to live by its provisions.

Russia insisted that the Americans couldn't demand Assad's departure. It also worried about opening the door to military action, even as Washington offered to include language in any U.N. resolution that would have expressly forbidden outside armed intervention.

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  • Turkey

    Turkey has struck the Syrian military repeatedly in response to shelling and mortar rounds from Syria since Oct. 3, when shells from Syria struck the Turkish village of Akcakale, killing two women and three children. The incident prompted NATO to convene an emergency meeting and Turkey sent tanks and anti-aircraft batteries to the area. Turkey's military has also scrambled fighter jets after Syrian helicopters flew close to the border. <em>Caption: Turkish soldiers patrols as Syrian nationals pass the border between Syria and Turkey on November 10, 2012, near the town of Ceylanpinar. (BULENT KILIC/AFP/Getty Images)</em>

  • Turkey

    There are about 120,000 Syrian refugees sheltering in Turkish camps, with up to 70,000 more living in Turkey outside the camps. Thousands more wait at the border, held up as Turkey struggles to cope with the influx. Turkey also hosts much of the opposition and rebel leadership. <em>Caption: A Syrian-Kurdish woman refugee sits in the courtyard of a house in the Turkish town of Ceylanpinar, bordering Syria, on November 10, 2012. (PHILIPPE DESMAZES/AFP/Getty Images)</em>

  • Turkey

    Turkey has called for a buffer zone in Syria where the opposition and civilians would be protected, a step that would likely require international enforcement of a no-fly zone. Russia and China have blocked robust moves against the Syrian regime at the U.N. Security Council, and the United States has been reluctant to use its military in another Mideast conflict. <em>Caption: Turkish soldiers patrols as Syrian nationals pass the border between Syria and Turkey on November 10, 2012, near the town of Ceylanpinar. (BULENT KILIC/AFP/Getty Images)</em>

  • Israel

    Israel on Monday became the second country to strike the Syrian military, after Turkey. An Israeli tank hit a Syrian armored vehicle after shells from fighting in Syria exploded in Israel-controlled Golan Heights. A day earlier, Israel fired a warning shot near a group of Syrian fighters. <em>Caption: Israeli tanks, one in position, the other getting into a firing position in the Israeli-controlled Golan Heights overlooking the Syrian village of Bariqa, Monday, Nov. 12, 2012. (AP Photo/Ariel Schalit)</em>

  • Israel

    Syrian shells have exploded inside the Golan several times in recent weeks damaging apple orchards, sparking fires and spreading panic but causing no injuries. In early November, three Syrian tanks entered the Golan demilitarized zone, and in a separate incident an Israeli patrol vehicle was peppered with bullets fired from Syria; no one was hurt in the incident and the Israeli military deemed it accidental. <em>Caption: Smoke rises after shells fired by the Syrian army explode in the Syrian village of Bariqa, Monday, Nov. 12, 2012. (AP Photo/Ariel Schalit)</em>

  • Israel

    There is concern in Israel that Assad may try to spark a conflict with Israel, opening up the potential for attacks by Lebanon's militant Hezbollah and Hamas in the Gaza Strip. Israel has also warned that Syria's chemical weapons could be turned on the Jewish state. Still, while no friend of Assad, Israel is also worried that if he is toppled, Syria could fall into the hands of Islamic extremists or descend into sectarian warfare. <em>Caption: Israeli troops and UN peacekeepers inspect on November 8, 2012 the area where three mortar shells fired from Syria landed in Alonei Habashan in the Israeli-occupied Golan Heights, which Israel seized from Syria in 1967. (JALAA MAREY/AFP/Getty Images)</em>

  • Lebanon

    Mortars and shells from the Syrian side regularly crash in Lebanon, causing several casualties, though Lebanese forces have never fired back. More dangerously, Syria's conflict has heightened deep rivalries and sectarian tensions in its smaller neighbor. Lebanon is divided between pro-Assad and anti-Assad factions, a legacy of the nearly three decades when Damascus all but ruled Lebanon, until 2005. Assad's ally, the Hezbollah militia is Lebanon's strongest political and military movement. <em>Caption: Lebanese army commandos deploy in the Bab al-Tabbaneh and Jabal Mohsen neighbourhoods where clashes are taking place between Sunnis and Alawites in the northern city of Tripoli on October 23, 2012. (JOSEPH EID/AFP/Getty Images)</em>

  • Lebanon

    On Oct. 19, a car bomb assassinated Lebanon's top intelligence chief, Wissam al-Hassan. Many in Lebanon blamed Syria and Hezbollah for the assassination. The northern Lebanese city of Tripoli has seen repeated clashes between Sunni Muslims and Alawites – the Shiite offshoot sect to which Assad belongs. Battles in the city in May and August killed at least 23 people total and wounded dozens. <em>Caption: A memorial poster of Brig. Gen. Wissam al-Hassan, who was assassinated Friday, hangs near the spot Friday's car bomb attack that killed Al-Hassan, in the Achrafieh district of Beirut, Lebanon, Tuesday, Oct. 23, 2012. (AP Photo/Maya Alleruzzo)</em>

  • Lebanon

    The kidnapping of Lebanese Shiites in Syria by rebels has also had repercussions in Lebanon. In May, Shiites blocked roads and burned tires in protest over the abductions, and later in the summer a powerful Shiite clan took 20 Syrians and a Turk in Lebanon captive in retaliation, all of whom have since been released. Lebanon also shelters about 100,000 Syrian refugees. <em>Caption: A Syrian man Firas Qamro, 31, who was injured during clashes that erupted between supporters and opponents of the Syrian regime, in the northern port city of Tripoli, Lebanon, Monday, Oct. 22, 2012. (AP Photo/Bilal Hussein)</em>

  • Jordan

    Jordan has taken the brunt of the refugee exodus from Syria, with some 265,000 Syrians fleeing across the border. Around 42,000 of them are housed at Zaatari, a dust-filled refugee camp, where riots have broken out several times by Syrians angry over lack of services. A growing number of stray Syrian missiles have fallen on Jordanian villages in the north in recent weeks, wounding several civilians. <em>Caption: In this Saturday, Sept. 15, 2012 photo, a Jordanian army vehicle carries Syrian refugees who have fled violence in their country having crossed into Jordanian territory with their families near the town of Ramtha. (AP Photo/Raad Adayleh)</em>

  • Jordan

    Late last month, a Jordanian border patrol officer was killed in clashes with eight militants trying to cross into Syria. Hours earlier, Jordan announced the arrest of 11 suspected al-Qaida-linked militants allegedly planning to attack shopping malls and Western diplomatic missions in Jordan. <em>Caption: Jordanian border soldiers guard newly-arrived Syrian refugee families after they crossed the border from Tal Shehab city in Syria, through the Al Yarmouk River valley, into Thnebeh town, in Ramtha , Jordan, Wednesday, Sept. 5, 2012. (AP Photo / Mohammad Hannon)</em>

  • Iraq

    Sunni and Shiite fighters from Iraq have made their way to Syria to join the civil war – the former on the side of the opposition, the latter siding with Assad's regime, according to Iraqi officials and Shiite militants. Sunni al-Qaida fighters are believed to be moving between Iraq and Syria, and some al-Qaida fighters in Iraq's western Anbar province have regrouped under the name of the Free Iraqi Army, a nod to the rebels' Free Syrian Army, Iraqi officials say. <em>Caption: In this Saturday, March 17, 2012 file photo, Syrian security officers gather in front the damaged building of the aviation intelligence department, which was attacked by one of two explosions in Damascus, Syria. (AP Photo/Bassem Tellawi, File)</em>

  • Iraq

    About 49,000 Syrian refugees have temporarily resettled in Iraq, according to the U.N. refugee agency. The United States has pressured Baghdad to stop Iranian planes suspected of ferrying arms to Syria from using Iraqi airspace. Iraq has so far acknowledged only forcing two planes to land for inspection and said it didn't find any weapons either time. <em>Caption: Syrian refugees rest as they have crossed the border by the Iraqi town of Qaim, 200 miles (320 kilometers) west of Baghdad, Iraq, Tuesday, Aug. 7, 2012. (AP Photo/Hadi Mizban)</em>