Israel tightened its grip on Jenin today, scouring the battered West Bank city for militants thought to have engineered suicide bombings, as a U.S. mission to contain two years of Middle East violence wound down indecisively.

Hundreds of troops backed by heavy armor rolled into Jenin on Friday, commandeering buildings, searching homes and imposing curfews. The army drew fire from local gunmen and, on the diplomatic front, from the European Union, which urged restraint.

Israeli military chiefs said the Jenin operation -- dubbed "Vanguard" -- would last as long as necessary to flush out militants using the bombings in an uprising against continued Israeli occupation of the West Bank and Gaza Strip. One such attack killed 14 Israelis on Monday.

Palestinian medics said six people were seriously wounded in clashes with the army -- violence that overshadowed the end of a two-day visit to Israel and the Palestinian territories by a U.S. envoy, William J. Burns.

Burns came with a "road map" for peace based on the vision of President Bush, and the widely anticipated American offensive on Iraq lent urgency to his mission to preserve good relations with the Arab world.

Apparently under U.S. pressure, Israel initially held back retaliation for Monday's bombing, which was carried out by two Jenin teenagers belonging to the militant group Islamic Jihad.

The were no apologies after the army incursion on Friday.

"Jenin has become the capital of terror," Israeli Defense Minister Binyamin Ben-Eliezer said. "When I speak of men and women suicide bombers, this is where they come from."

Palestinian censure soon followed. Nabil Abu Rdainah, adviser to the Palestinian leader, Yasser Arafat, said that Israel had "sabotaged U.S. efforts regarding the road map plan."

The U.S. plan calls for an end to violence, for Palestinian administrative reforms and for Israeli army withdrawals from occupied cities, leading to a final settlement and a Palestinian state in the West Bank and Gaza Strip by 2005.

At least 1,629 Palestinians and 618 Israelis have been killed since the uprising began in September 2000 after talks on Palestinian statehood stalled.

Israeli leaders said the plan, drafted by mediators from the United States, Russia, the European Union and United Nations, lacked security guarantees. The Palestinians said it needed timetables and enforcement mechanisms.

Burns met Israeli Prime Minister Ariel Sharon Thursday evening in Jerusalem to discuss the U.S.-led peace plan. Israel has given the plan a cool reception, while Palestinian officials said they would deal positively with the ideas.

Elsewhere, there were signs on the ground of tensions easing.

The army suspended curfews in the West Bank cities of Nablus, Tulkarm and Qalqilyah and said that troops stationed in Palestinian areas of divided Hebron were gradually pulling out after getting security assurances from the Palestinian governor. The governor of Hebron, Aref Jabari, denied the report.