Jerusalem ? Israeli tanks entered the West Bank town of Jenin Friday morning and patrolled the outskirts of Bethlehem before daybreak, witnesses said, underlining Israel’s intention to maintain a high-profile military presence after a string of Palestinian attacks.

About 20 tanks rolled into Jenin, at the northern edge of the West Bank, the witnesses said. Soldiers declared a curfew, confining residents to their homes. The Israeli military called the operation a “routine patrol.” Israeli forces also declared curfews in five villages near Jenin, residents said.

A teen-age bomber who blew up an Israeli bus with an explosives-laded car on Wednesday set out on his mission from Jenin. The Islamic Jihad claimed responsibility, but Israel blamed Palestinian leader Yasser Arafat, charging that he has done nothing to stop the attacks.

Israeli forces patrolled along the southern edge of Bethlehem early Friday but did not enter the town, the military said.

Early Thursday, Israeli tanks and bulldozers crashed into Arafat’s headquarters in the West Bank town of Ramallah and destroyed three buildings in a raid the Israeli military said was a response to the bombing attack, which killed 17 Israelis at an intersection in northern Israel.

An Israeli teen-ager from the Jewish settlement of Ofra, between Ramallah and Nablus, was shot and killed Thursday in a roadside ambush.

The spiritual leader of Hamas, Sheik Ahmed Yassin, said the organization would continue attacks inside Israel, despite a call from Arafat to stop them.

“We shall continue to pursue them (Israelis) everywhere, and they will not have security as long as we don’t have it,” he said in an interview published in the Lebanese newspaper An-Nahar on Friday, repeating the Hamas view that Israel belongs to the Palestinians.

The daily violence and counterstrikes threatened to undermine new U.S. efforts to bring an end to more than 20 months of fighting. In the past week, two top-level U.S. officials have visited for talks with Israeli and Palestinian leaders.

Israeli Foreign Minister Shimon Peres said a key part of a new U.S. peace formula could be a settlements-for-refugees trade.

“There is something new emerging in the U.S. which says that the Palestinians will give up on the right of return (of refugees and their descendants to their original homes in Israel) in exchange for Israel giving up on all the settlements” in the West Bank and Gaza Strip, he said. He told Israel Radio on Friday that this was not an official administration plan.

U.S. officials did not comment directly. State Department spokesman Richard Boucher said “we are listening” to what various leaders have to say.

Israeli Prime Minister Ariel Sharon is to meet President Bush in Washington on Monday. Sharon delayed his departure after the bus bomb attack, ordering Israeli forces to retaliate by hitting Arafat’s headquarters.

The Palestinian Authority, headed by Arafat, denounced the bombing and ordered the arrest of Islamic Jihad activists. Even so, the group’s leader, Abdullah Shami, remained at his home in Gaza, apparently unconcerned. Palestinian security officials said they could not carry out the arrest order because Israel had destroyed Palestinian prisons in air strikes.

After the raid on Arafat’s compound early Thursday, the Israeli military issued a statement holding Arafat responsible for “a wave of Palestinian terrorism that has swept the state of Israel” and pledged military operations aimed at rooting it out.

However, the almost nightly raids on Palestinian areas were not enough for many Israelis, including some Cabinet ministers who clamored for Israel to expel Arafat.

Finance Minister Silvan Shalom, from Sharon’s Likud party, told Israel TV that soon a majority of Israel’s Cabinet will support expelling Arafat. “When I first proposed it, they thought I was eccentric,” he said.

Sharon adviser Raanan Gissin said that for now, Arafat’s ouster was not being contemplated. “His expulsion would not solve the problem. The security services do not recommend this as the most effective solution,” he said.

White House spokesman Sean McCormack agreed. “I don’t think exiling Arafat solves anything,” he said.

Arafat dismissed the expulsion threat, talking to reporters after taking them on a tour of his damaged headquarters. “Expel me?” he laughed. “I will die here.”