INAT CAMP, West Bank, April 10 — A day ahead of Secretary of State Colin L. Powell's arrival in Israel in hopes of securing a truce, a Palestinian suicide bomber attacked an Israeli bus today and Prime Minister Ariel Sharon vowed to continue Israel's military sweep through the West Bank.

Rebuffing American demands for a withdrawal, Mr. Sharon said the United States and other nations should not "put any pressures upon us."

Mr. Sharon addressed soldiers at this improvised hilltop base overlooking Jenin, a Palestinian city where Israel pressed its offensive today by sending armored bulldozers crashing through the densely populated refugee camp.

Late tonight, an Israeli official said as many as 200 Palestinians had been killed in Jenin. Most, he said, were armed men. Palestinian resistance in Jenin, the fiercest that Israeli forces have encountered, appeared to be ebbing.

Israeli forces withdrew from three West Bank villages today, Yatta, Qabatya and Samua, but continued hunting suspected militants in four major cities and towns and an undisclosed number of other villages. Late tonight, Israeli tanks moved into Ber Zeit, a village in the central West Bank, The Associated Press reported.

Earlier in the day, Israel's security cabinet formally decided to continue the military operation, now nearly two weeks old. It acted after the suicide bomber struck, killing eight passengers and tearing apart a bus near Haifa, on the coast. Four of the dead were soldiers.

It was the first suicide attack in 10 days. For some it underscored the crying need they saw for Israel's military mission, and for others the folly they saw at its core.

Along Israel's embattled northern border, more missiles and mortar bombs were fired from Lebanon, despite American efforts to persuade Syria to restrain the militant Lebanese group Hezbollah. The attacks injured no one but fed fears of a widening conflict, further complicating Secretary Powell's difficult mission.

The secretary is arriving late Thursday at a moment filled with hostility and mistrust, burdened by the numbers of casualties on both sides, the bitter enmity of the leaders and the spreading separation of the two peoples.

Palestinian families have been hiding in their homes as Israeli patrols round up their men for questioning and Israeli machine-gun fire pounds through their streets. Israelis, despairing of Palestinian willingness to recognize a Jewish state, have been avoiding cafes, parks and malls for fear of suicide bombers.

After resisting becoming entangled here, President Bush reversed course and dispatched Secretary Powell as the body count grew and he came under pressure from Arab states, whose backing he is seeking for a possible attack on Iraq. The anxiety of Israeli officials over the Bush administration's evolving policy also increased today as the country's diplomatic predicament worsened.

The European Parliament urged the 15 members of the European Union, Israel's biggest trading partner, to impose sanctions against Israel because of the military operation.

Here at the military camp, Mr. Sharon warned about 50 soldiers sitting in the dirt beneath an awning here, their M-16 rifles in their laps: "We are in a diplomatic battle. Arab countries are pressuring the U.S. and European countries as much as they can in order to make Israel carry out a plan or plans that we can't."

He described Israelis as victims in a multifront war, a fight against terrorism, a "diplomatic struggle" and a "public opinion battle."

"We are the victims of terror," Mr. Sharon told the soldiers. It was a war Israel did not want or start, he said. "But we got to a situation where we couldn't deal with it anymore," he continued. "The terrible thing, and it is perhaps the cynicism of the world, is that the one being blamed, is particularly us."

The isolation of Yasir Arafat eased a bit today when Israel permitted other Palestinian officials to enter his besieged compound in Ramallah. The Palestinians then met in Jerusalem with Gen. Anthony C. Zinni, the Bush administration's special envoy here, to prepare for Secretary Powell's arrival. Israel had previously blocked General Zinni from meeting with the group.

Secretary Powell has said he wanted to meet with Mr. Arafat, a decision Mr. Sharon has called a "tragic mistake." Mr. Sharon considers Mr. Arafat an enemy of Israel, not a potential negotiating partner.

But Israel's defense minister, Benjamin Ben-Eliezer, said the government would not interfere with the secretary's plans. "As long as Powell wants to see Arafat, he can see him," Mr. Ben-Eliezer said after sitting at the prime minister's right hand during his remarks here. "We are not preventing him to see Arafat."

About 300 Palestinians surrendered in Jenin today, Israeli officials said. Witnesses described masses of women and children fleeing the refugee camp as bulldozers cut through the ramshackle warren of adjoining and stacked homes.

"Vietnam — something like that," said Eitan Gafni, a reserve soldier serving here, describing the condition of the refugee camp to Israeli television. "There's nothing there now."

In an overwhelming display of force within easy sight of Jenin, dozens of Israeli armored vehicles and tanks waited in a camp gouged out of the hillside, below where Mr. Sharon spoke late this afternoon.

At a checkpoint a mile or so away, mobile antiaircraft guns were parked, and mechanics worked on one engine. The soldiers said that they had served in the Israeli campaign in three cities, from Ramallah to Nablus to Jenin, and that the fighting had grown fiercer as they moved to each new front.

The Israeli Army continued to block journalists from entering Jenin, saying it feared for their safety. But Israeli officials were also nervously looking ahead to the eventual withdrawal, fearful that Palestinians would try to present the many corpses as evidence of an Israeli massacre.

Palestinians accuse Israeli ground forces of firing randomly into their neighborhoods. But many soldiers and Israeli officials said the Israeli Army was acting morally, and was even endangering its own men by applying force cautiously in an effort not to harm civilians.

Israelis are troubled by the world's perception of the military mission.

"I've seen pictures of us on the television, and we don't look very good," said Sgt. Dov Rifken, 20. But, he said, "we're supposed to protect our people, our country. We do what we need to do, and we make sure that's all we do."

The Palestinians have no military aircraft. They have been fighting mostly with semiautomatic rifles, homemade explosives and some mass-produced explosives like antitank weapons. Israel has been using the antiaircraft weapons, capable of shooting 3,000 20-millimeter rounds a minute, to pulverize houses containing gunmen.

"If we see some people shooting from a house, we take it down," Sergeant Rifken said.

In Jenin, said Cpl. Yaron Zeltzer, 20, "the Palestinians were really prepared, and there was a much more tough section of terrorists." The Palestinians had concealed booby traps in sewers and other unexpected places, he said.

On Tuesday 14 soldiers were killed in Jenin, 13 in an ambush. Another soldier died in Nablus on Tuesday, the victim of mistaken fire from Israeli forces.

Mr. Ben-Eliezer, the defense secretary, said he could not predict how much longer Israel would continue its military operation. But it was too early to stop, he said. "We can just evacuate today, and tomorrow the suicide bombers, the suicide shooters, will move again," he said.

Asked how Palestinians were able to carry out today's suicide bombing in Haifa, he said the Israeli operation could minimize terrorist capabilities and "destroy for a while the motivation" of attackers, but "there is no 100 percent answer to terror — no."

Palestinian officials say that rather than suppressing the motivation for such attacks, the Israeli operation is likely to feed it.

The Islamic group Hamas claimed responsibility for the Haifa bombing and attributed it to a Palestinian from the Jenin refugee camp. Hamas is opposed to a two-state solution to the Israeli-Palestinian conflict, and it has engineered suicide attacks during previous diplomatic missions by General Zinni.

Those missions also coincided with halts in Israeli incursions into Palestinian-controlled territory that had resulted in many Palestinian deaths.

Some Israeli officials said the bomber had come from Tulkarm, where Israeli soldiers have withdrawn to form a cordon around the city. They dismissed any suggestion that the bombing undermined claims for the success of the mission, saying it actually demonstrated the dangers of withdrawing.

But in Washington, Ari Fleischer, the White House spokesman, suggested that the bombing showed the wisdom of President Bush's call for a withdrawal. Mr. Fleischer said the attack underscored "the need for all parties to step back, for Israel to withdraw, and for the Palestinians and the Arabs to stop the violence, stop the killing."

The comment stunned Israeli officials, who read it as suggesting that the Israeli action provoked rather than prevented terrorism. "It legitimizes terror," one Israeli official said.

This official, who insisted on anonymity, expressed consternation at what he viewed as a reversal of American policy, from apparent support of the Israeli operation to Mr. Bush's demand, first made last Thursday, for withdrawal. "Do they want to go into a collision course with Israel?" he asked.

Secretary Powell plans to meet with Mr. Sharon before seeing Mr. Arafat. Israel offered Mr. Arafat the chance to hold the meeting in Jericho, which has not been raided by the army during this operation, rather than in battered Ramallah, in an office that is said to have turned rancid.

Such a move might also suit Israel purposes, one official acknowledged, since the pictures might be prettier in Jericho and Israel might even have the chance to raid Mr. Arafat offices, where military officers believe he is hiding wanted men.

Mr. Arafat declined the offer of a different venue, the Israeli official said.