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Expanding "Operation Protective Wall," Israeli tanks rolled into the West Bank's largest city, Nablus, on Wednesday and other troops laid siege to a refugee camp in Jenin, battling Palestinians who barricaded entrances and fought back with bombs and guns.

In biblical Bethlehem, just south of Jerusalem, Israeli and Palestinian officials failed to resolve a standoff at the Church of the Nativity, built over the site where tradition says Jesus was born and one of Christianity's major shrines.

Twelve Palestinians and an Israeli soldier were killed on the sixth day of Israel's offensive aimed at crushing Palestinian militias and stopping terror attacks on Israeli civilians.

Shortly before midnight, Israeli Prime Minister Ariel Sharon convened the Security Cabinet, made up of his most senior ministers, to approve the next stage of the open-ended operation. Only two major West Bank towns — Hebron and Jericho — were still under Palestinian control late Wednesday. No details about the meeting were immediately available.

President Bush repeated his support for the Israeli assault. "He understands and respects Israel's right to defend herself," White House spokesman Ari Fleischer said. Secretary of State Colin Powell said he was weighing a meeting with Israeli and Arab leaders during a trip to Europe next week.

A great deal of focus remained on Bethlehem, where about 300 Palestinians, nearly all of them armed, have been holed up in the Church of the Nativity since Tuesday, running from Israeli forces after hours of heavy gun battles near the church and adjacent Manger Square.

Israeli Defense Minister Binyamin Ben-Eliezer said Israel did not intend to break into the church, but army officials said those inside would not be allowed to go free. Five Italian journalists and an Armenian colleague, who had been trapped in the church compound by the fighting, were evacuated Wednesday.

One of the Italian journalists, RAI TV correspondent Marc Innaro, said the gunmen "were very determined, not nervous, tired also, but not willing at all to surrender."

More than a dozen leaders of Christian churches in the Holy Land, including Latin Patriarch Michel Sabbah, tried to reach Bethlehem on Wednesday, but were turned away at an Israeli military checkpoint.

Several dozen Palestinians, including some who were armed, also sought sanctuary at St. Mary's, a Roman Catholic convent near Manger Square. At one point Wednesday, a priest and seven nuns emerged from the convent, but by then the gunmen had slipped out the back, the army said. The Israeli army spokesman, Brig. Gen. Ron Kitrey, said the bound body of Palestinian man wearing a camouflage jacket was found in the building, and that the circumstance of his death were not immediately clear.

The bodies of five more Palestinians, including at least two gunmen, were found elsewhere in Bethlehem.

Powell has been sending increasing signals that he is considering heightening his involvement in the troubled region.

"My mind is open," Powell told reporters at the State Department. "We are examining all possibilities. I would not rule out meeting with anybody where it would serve a useful purpose."

Powell later said in an interview with CBS' 60 Minutes II that it was not out of the question that he would go to the Middle East.

Also, Powell said, he intends to step up his efforts to have a Palestinian state emerge quickly, once negotiations are resumed.

"The Palestinian people have to see that there is a political process, and not just a cease-fire and security process ... which will lead quickly to a Palestinian state," Powell said.

The European Union, meanwhile, said it would send a high-level mission to the Middle East to urge the sides to open negotiations. The move came hours after top EU official Romano Prodi criticized U.S. peace efforts, asking Washington to stand down and make room for other nations to try.

U.S. special envoy Anthony Zinni remains in the region striving to implement a truce plan authored last June by CIA chief George Tenet. The U.S. Embassy hasn't released any information on his activities in recent days, and no meetings were scheduled with either Israelis or Palestinians.

But daily anti-Israeli protests in the Arab world grew more violent. Thousands of Lebanese and Palestinians clashed with security forces Wednesday outside the U.S. Embassy in Beirut, with at least 25 reported injured as protesters threw stones and security forces used tear gas and water cannons.

Under pressure to cut off ties completely with Israel, Egypt took a more limited step Wednesday, announcing it would suspend all diplomatic contacts with Israel except those aimed at helping the Palestinians.

In New York, the U.N. Security Council debated a Palestinian-backed resolution aimed at pressuring Israel to withdraw from its cities but deferred voting until at least Thursday.

In five major Palestinian towns under full Israeli control — Ramallah, Qalqiliya, Jenin, Tulkarem and Bethlehem — tanks patrolled streets, enforcing strict curfews that confined hundreds of thousands of Palestinians to their homes. In Ramallah, residents were without water after city officials said Israeli troops destroyed the main pumping station when shelling a Palestinian security compound.

Violence flared at a checkpoint outside Ramallah as Israeli police fired tear gas Wednesday to hold back more than 2,000 Israeli activists — Jews and Arabs — who were trying to deliver humanitarian supplies to Ramallah.

The incursion into Nablus — a city of more than 100,000 people in the northern West Bank — began Wednesday evening. Shellfire thundered as tanks began rolling into the city. Gunmen and Palestinian police were moving in the streets, closing roads with sandbags and planting mines.

A woman was killed in an explosion in Nablus, residents said, but it wasn't immediately clear if she died from Israeli fire or from a bomb being prepared by a militant went off accidentally. Five people were wounded, apparently when shells hit two apartments in downtown Nablus. Israeli forces, backed by attack helicopters, surrounded the four Palestinian refugee camps next to the city, witnesses said, and there were exchanges of fire. The Israeli military had no comment.

Fighting was heaviest Wednesday in Jenin, a militant stronghold north of Nablus that Israel has invaded six times before in the past 18 months of fighting.

Dozens of tanks entered Jenin and surrounded the adjacent refugee camp early Wednesday. Helicopters and tanks fired machine guns at gunmen who hurled grenades and fired from assault rifles. Five people, including a militia leader, a nurse and a 13-year-old boy, were killed in the fighting. An Israeli officer was also killed.

Ali Safouri, a militia leader, said he and his men felt that, judging by Israel's tough sweep through Ramallah, this was their last stand. He said they were trying to make every bullet count. "We use it for sniping only, we are not shooting in all directions," Safouri said by telephone.

In Ramallah, Palestinian leader Yasser Arafat remained a prisoner of Israel, confined to a few rooms in his former headquarters. Raanan Gissin, a Sharon adviser, said Arafat "won't communicate [with the outside world] until ... we see he is no longer a threat and not instigating terrorism."

Arafat, who is accompanied by about 300 people, including aides, security guards and several dozen foreign volunteers, still has use of a mobile phone. Israel insists it is trying to keep him relatively comfortable.

Israeli President Moshe Katsav, meanwhile, expressed support over Israel Radio for a fence between Israel and the West Bank to stop suicide bombers.

The Associated Press contributed to this report.