WASHINGTON - Under mounting pressure from President Bush, Israel began withdrawing early this morning from two of the six West Bank cities it has occupied during its broad military offensive to suppress Palestinian violence and terrorism.
The move marked the first break in a four-day test of wills between the president and Prime Minister Ariel Sharon of Israel. Bush had demanded a withdrawal from the West Bank. But Sharon refused to cut short a military operation that he said had destroyed terrorist facilities and produced the arrests of 500 fugitives "with Israeli blood on their hands."
"It's a start," Ari Fleischer, Bush's spokesman, said after Israel announced that its forces would begin pulling out of Tulkarm and Qalqiliya, two towns along the border between Israel and the Palestinian territories.
But elsewhere in the West Bank, Israeli troops pressed ahead aggressively, particularly in Jenin and Nablus.
Witnesses said troops and tanks began a fresh incursion into the southern West Bank town of Dora shortly after the pullout started. Tanks and armored personnel carriers rolled into the town before dawn as helicopters provided cover, and gunbattles could be heard.
The fighting was heaviest in Jenin, where Palestinians say huge armored bulldozers knocked down homes on top of people living in them, to widen narrow alleys so tanks could pass. The army said helicopters fired at least 20 missiles at targets in the Jenin refugee camp, home to about 15,000 people. Casualties were reported to be heavy, though exact numbers were not available. Two Israeli soldiers were killed, and another was seriously wounded.
In Nablus, about 100 gunmen surrendered to Israeli troops while scores more lay wounded on blankets on the floor of a mosque. Some of the men were dying, and doctors lacking even the most basic supplies operated on others without anesthetics.
And the Israelis showed no sign of easing a siege of the Church of the Nativity in Bethlehem, where Palestinian fighters are holed up.
In a speech to parliament earlier yesterday, Sharon said that Israel's offensive was a necessary response to a "murderous insanity which has taken hold of our Palestinian neighbors."
And the prime minister vowed to continue the operation "until the mission has been accomplished, until [Yasser] Arafat's terrorist infrastructures are uprooted" and terrorists hiding in places like the Bethlehem church are captured.
The Israeli offensive, in which more than 200 Palestinians have been killed, has caused a crisis in the Arab world. It has also raised fears in the Bush administration of growing regional unrest that could escalate threats to Israel over the long term and bury any hope of a renewed peace process.
Those concerns, in part, led Bush to dispatch Secretary of State Colin L. Powell to the region to try to broker a cease-fire and try to pave the way for eventual peace negotiations between Israel and the Palestinians.
"We're looking to have things move in the right direction by the time the secretary arrives" in Israel later this week, an administration official said.
Hours before Israel announced that it would begin a partial pullout, Bush sought to dispel any doubt that he was resolute in his demand for a withdrawal, which he first made in a speech Thursday and repeated in a phone call to the prime minister Saturday.
"I meant what I said to the prime minister of Israel," Bush said sternly in a brief statement in Knoxville, Tenn. "I expect there to be a withdrawal without delay."
The United States' envoy, Gen. Anthony C. Zinni, made the same demand yesterday during a meeting with Sharon.
At the same time, the president demanded action by Arab leaders, saying: "I also meant what I said to the Arab world - that in order for there to be peace, nations must stand up, leaders must stand up and condemn terrorism."
The Israeli incursion followed a spate of suicide bombings, including an attack March 27 at a hotel dining room on Passover that left 27 Israelis dead.
In his speech, Sharon said that once Israeli troops withdraw from the Palestinian cities, they will set up buffer zones between Palestinian and Israeli territories "in order to prevent any penetration into Israeli communities, attacks on Israeli civilians and threats to our security."
The United States has sent conflicting messages about the Israeli offensive. The day after the military operation began, Bush declared that Israel's government had the right to decide how to defend its citizens. And he avoided mentioning a United Nations Security Council demand, backed by the United States, for a pullout.
On Thursday, the president called on Israel to begin a withdrawal from the six West Bank cities but did not specify a deadline. On Saturday, Bush demanded that Israel begin a withdrawal "without delay."
Analysts say the shifts have given rise to widespread questions in the region about Bush's real expectations.
In the Arab world, "they will assume there is some kind of agreement" between Bush and Sharon to allow Israel to continue the operation, said Edward Walker, a former assistant secretary of state for the Near East.
Yossi Alpher, an Israeli strategic analyst, said Sharon might not have been convinced that the Bush administration is united and serious about pressing for an end to the operation. Noting that neither Vice President Dick Cheney nor Defense Secretary Donald H. Rumsfeld has spoken out publicly, Alpher said the Israeli government might have concluded that the administration is divided and that "the hawkish wing doesn't appear to have its heart in the demand" for withdrawal.
If Bush did nothing in the face of Sharon's defiance, he would look weak, said Philip Wilcox, a Middle East specialist who formerly was the State Department's top counter-terrorism official. "I don't believe, in the end, Bush will stand for that."
The military operation has been broadly popular among the traumatized Israeli populace and has sharply increased Sharon's standing in the polls.
At the same time, Wilcox said, "Sharon is not stupid. He may realize that he can't afford a confrontation with the United States. In the end, it plays very badly with the larger Israeli public."
The United States has demanded that Israel ease its isolation of Arafat so the Palestinian leader can consult with his advisers about cease-fire plans presented by Zinni.
Although he had hinted at a boycott of Arafat, Powell said yesterday that he hoped to meet with the Palestinian leader. He has said he also plans to meet with other leaders.
On his first stop in the Arab world yesterday, Powell received a chilly reception from King Mohammed VI of Morocco, who asked why he had not headed first to Jerusalem to push for an Israeli troop pullback.
Powell is trying to enlist Arab leaders in pressuring Arafat to speak out publicly in Arabic against suicide bombings, in addition to agreeing to a cease-fire. After meeting with the king in Casablanca, Powell was to see Saudi Crown Prince Abdullah bin Abdul Aziz, who is vacationing in the city.
Wire reports contributed to this article.