* Israeli tanks and troops roll into small coastal enclave
* Israel focused on Hamas tunnels, ready for long haul
* Palestinian civilian toll mounts; Hamas fights, defiant
* France asks Qatar to help secure ceasefire (Updates casualty toll, adds U.N. chief to travel to region)
By Nidal al-Mughrabi and Jeffrey Heller
GAZA/JERUSALEM, July 18 (Reuters) - Israel warned on Friday it could "significantly widen" a Gaza land offensive but was cautioned by its main ally, the United States, about the risks of further escalation as Palestinian civilian deaths mounted.
Palestinian officials said 58 Palestinians, at least 15 of them under the age of 18, have been killed since Israel sent ground forces on Thursday into the densely-populated enclave of 1.8 million Palestinians.
The Israeli military said it killed 17 Palestinian gunmen while another 13 surrendered and were taken for questioning after the infantry and tank assault began in the Islamist Hamas-dominated territory.
One Israeli soldier was killed in an apparent friendly fire incident, the military said, and several other troops were wounded in the ground operations. It said some 150 targets, including 21 concealed rocket launchers and four tunnels, have been attacked.
U.S. President Barack Obama said on Friday he had spoken to Prime Minister Benjamin Netanyahu, underscoring Washington's support for Israel to defend itself but raising concerns about "the risks of further escalation" and additional loss of innocent lives.
"We are hopeful that Israel will continue to approach this process in a way that minimizes civilian casualties," Obama told reporters at the White House.
U.N. Secretary-General Ban Ki-moon planned to travel to the Middle East on Saturday in a bid to end the hostilities.
At an emergency session of the U.N. Security Council on Friday, U.N. political affairs chief Jeffrey Feltman condemned rocket fire into Israel but voiced alarm at "Israel's heavy response".
The Israeli land advance followed 10 days of barrages against Gaza from air and sea, hundreds of rockets fired by Hamas into Israel and failed attempts by Egypt, a broker of ceasefires in previous Israeli-Palestinian flare-ups, to secure a truce.
After nightfall on Friday, flares fired by Israeli forces cast an orange glow above the coastal enclave as explosions echoed in what appeared to be intensified Israeli attacks from the air and ground.
Rocket salvoes, many of them intercepted by the Iron Dome anti-missile shield system, continued on Friday against southern Israel and the Tel Aviv metropolitan area, police said, causing no casualties.
"We chose to start this operation after we exhausted other options and reached the conclusion that without it we could pay a much higher price," Netanyahu told reporters before a special cabinet session at Tel Aviv military headquarters. "The main goal is to restore quiet.
"My instructions...to the Israeli army, with the approval of the security cabinet, is to prepare for the possibility of a widening, a significant widening of the ground operation."
He did not say what form a broadened offensive might take. Israel says its forces have focused so far on seeking out tunnels Palestinian militants might use for cross-border raids and moving weaponry.
One such infiltration was narrowly thwarted on Thursday, with the army saying it had repelled 13 Hamas gunmen after they emerged from a tunnel close to an Israeli farming community.
In all, 291 Palestinians - most of them civilians, of whom at least 50 were under the age of 18 - have been killed since fighting began on July 8, Gaza officials said.
There have been two Israeli fatalities - the soldier and a civilian, who was killed by a rocket. More than 100 rocket bursts a day at southern Israel and the heartland Tel Aviv area have sent hundreds of thousands dashing for shelters.
Gaza residents said Israeli forces has moved several hundreds meters (yards) into the north of the enclave and their deployment in the south of the territory was slightly deeper.
Hamas said its men were hitting Israeli tanks with mortar rounds and setting off bombs against troops crossing the sandy frontier under smokescreens.
To back up regular forces, Israel said it was calling up 18,000 military reservists, adding to 30,000 already mobilized. Abu Ubaida, spokesman for Hamas's armed wing, said it had thousands of fighters of its own "waiting to join the battle".
Hamas wants Israel and Egypt, whose military-backed government is at odds with the Palestinian Islamists, to lift border restrictions that have deepened Gaza's economic hardship and unemployment.
Israel briefly halted its Gaza assaults on Tuesday after accepting an Egyptian truce proposal. But Hamas, an offshoot of the outlawed Muslim Brotherhood in Egypt, said the plan failed to address its demands on ending the border blockades and releasing hundreds of its activists in the occupied West Bank activists held by Israel.
A U.S. official said Secretary of State John Kerry had been in regular contact with the foreign minister of the Gulf Arab state of Qatar, which has close links with Hamas, and other leaders "on how to get a ceasefire".
Qatar has suggested it take over as mediator but the U.S. and Israel say it is too close to Hamas to take on that role.
"In all his recent calls, the Secretary has made clear that we support the Egyptian proposal, and that we hope that everyone can get behind it," the official said. "There are no other serious ceasefire proposals being discussed."
Kerry's position was echoed by Amos Gilad, a senior Israeli Defense Ministry official who has held talks with Egypt's military-backed government on Cairo truce plan.
"It is important for Qatar to understand that an alternative initiative would be useless," he said on Israel's Channel 10 TV. "Let's be realistic: who borders Gaza - Qatar or Egypt?"
Egyptian Foreign Minister Sameh Shukri, speaking at a news conference with his French counterpart Laurent Fabius, called on all sides to accept Cairo's ceasefire initiative.
"We are working to find a framework so that both sides agree," Shukri said.
Though they are die-hard enemies, Israel says it does not intend to topple Hamas, the dominant Islamist force in Gaza.
The current conflict - the worst warfare between Israelis and Palestinians in two years - was stoked by the killing of three Israeli teens in the West Bank last month and the death on July 2 of a Palestinian youth in a suspected revenge murder.
Israel last mounted a large-scale invasion of the Gaza Strip during a three-week war in late 2008 and early 2009 that claimed 1,400 Palestinian and 13 Israeli lives. (Additional reporting by Noah Browning in GAZA, Stephen Brown and Annika Breidthardt in BERLIN and John Irish in CAIRO and David Brunnstrom in WASHINGTON; writing by Jeffrey Heller; editing by Philippa Fletcher)
BEFORE YOU GO
08/08/2014 2:47 PM EDT
White House Concerned By Renewed Fighting
The White House on Friday urged Israel and the Palestinians to resume talks and do what they can to protect civilians after Egyptian-mediated negotiations failed to extend a ceasefire and rocket fire resumed.
"The United States is very concerned about today's developments in Gaza," White House spokesman Josh Earnest told reporters.
"We condemn the renewed rocket fire and we are concerned about the safety and security of civilians on both sides of that conflict," he said.
08/08/2014 1:42 PM EDT
Official: 5 Palestinians Killed In Gaza
Five Palestinians, including a 10-year-old boy, have been killed in Israeli airstrikes on Gaza since a ceasefire fell apart on Friday, a Palestinian medical official reported to Agence France Presse.
Meanwhile, the Israeli army said Palestinian militants fired 35 rockets into Israel on Friday, injuring a soldier and a civilian.
The father of a ten-year old Palestinian boy, who was killed in an Israeli air strike on the Sheikh Radwan neighbourhood in northern Gaza City, mourns at the city's Al-Shifa hospital, on August 8, 2014. (MOHAMMED ABED/AFP/Getty Images)
08/08/2014 9:23 AM EDT
Palestinian Delegation Says Gaza Talks Will Continue
Palestinian factions will remain in Cairo and press on with Egyptian-mediated talks despite the end of the ceasefire in Gaza, the head of the delegation, Fatah official Azzam Ahmed, said on Friday.
"We are not for escalation. We are ready to continue through our Egyptian brothers in negotiating to reach a final agreement that would return the rights to their owners," Ahmed said. "I mean here lifting the blockade of Gaza."
Ahmed said Palestinian negotiators were due to meet Egyptian intelligence officials, who have been mediating the talks, later in the day. He said Palestinian factions were united in their decision not to extend the 72-hour truce that ended at 0500 GMT and had been clear about their basic demands to end the conflict.
08/08/2014 9:13 AM EDT
Egypt: Agreement Close In Gaza Talks
Egypt called on Friday for an immediate resumption of the ceasefire in Gaza and a return to the negotiating table, saying that only a few outstanding issues remained in negotiations it was mediating between Israel and the Palestinians.
"The foreign ministry calls on all sides to rise to their responsibilities ... and to return immediately to the ceasefire commitment and exploit the opportunity available to resume negotiations on the very limited sticking points that remain in the fastest possible time," the foreign ministry said in a statement.
08/08/2014 3:58 AM EDT
Israeli Airstrikes On Gaza Resume
BREAKING: Israel says it's resumed strikes on Gaza in response to rocket fire, after end of 3-day truce.— The Associated Press (@AP) August 8, 2014
08/08/2014 3:02 AM EDT
Cease-Fire Ends With New Rocket Attacks
A 72-hour cease-fire expired at 8 a.m. today, and not long after, Gaza militants began firing rockets at Israel, The Associated Press reported.
The Israeli military said at least 10 rockets had been fired at Israel since the truce ended. Prior to the attacks, a senior official for Hamas said the militant groups would not extend the cease-fire.
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08/06/2014 2:46 PM EDT
Official: Israel Agrees To Extend Ceasefire
Israel has conditionally agreed to extend a ceasefire that ended a month of fighting in Gaza beyond a Friday deadline, an Israeli official said on Wednesday, speaking on condition of anonymity.
The official did not say for how much longer Israel had agreed to extend the truce, only that: "Israel has expressed its readiness to extend the truce under its current terms," referring to the deal brokered by Egypt that took effect on Tuesday.
Hamas had no immediate comment.
08/06/2014 2:12 PM EDT
IDF: Rocket Sirens Were False Alarm
IDF confirms rocket sirens in southern Israel were false alarm http://t.co/QN677jtlXE— Haaretz.com (@haaretzcom) August 6, 2014
08/06/2014 1:18 PM EDT
Report: Rocket Sirens Sound At Gaza Border
ABC Foreign Editor Jon Williams reports that the IDF have confirmed the rocket sirens are sounding, but are checking to see if it is a false alarm.
08/05/2014 4:20 PM EDT
Israel Arrests Kidnapping Suspect
Reuters reports that Israel has arrested one of the suspects in the kidnapping and killing of three Israeli teenagers in the West Bank in June.
Hussam Kawasme, a 40-year-old resident of the West Bank city of Hebron, was arrested on July 11 in connection with the killing of Israelis Gil-Ad Shaer, Naftali Fraenkel and Eyal Yifrah, who went missing on June 12 and were discovered dead a couple of weeks later.
Their kidnapping sparked a cycle of violence that led to the month-long conflict between Israel and Palestinian militants in the Gaza Strip.
Kawasme's arrest was made public for the first time on Tuesday in a document from an Israeli court case over whether houses belonging to him and two other suspects - who remain at large - should be destroyed as a punitive measure.
The lawyers listed as representing Kawasme were not reachable for comment.
The court document said Kawasme had admitted to helping to organize the kidnapping - securing funding from the Hamas Islamist group in Gaza and purchasing weapons which he passed on to the two other suspects who carried out the attack.
Kawasme also helped to bury the bodies of the teenagers in a plot of land he had bought a few months earlier, it said.
Israel has named the other two suspects in the case as Marwan Kawasme and Amar Abu Aysha.