Israel (search) and the Palestinians pushed forward with efforts to arrange a summit between their leaders Sunday, while a U.S. envoy arrived in the region to try to revive long-stalled peace talks.

Senior Palestinian negotiator Saeb Erekat was to meet Sunday with Dov Weisglass, the chief of Prime Minister Ariel Sharon's (search) office, to lay the groundwork for a meeting between Sharon and Palestinian Prime Minister Ahmed Qureia (search).

The meeting came despite a threat by Qureia not to participate in peace negotiations if Israel does not halt construction of a West Bank security barrier.

Meanwhile, U.S. envoy William Burns was scheduled to meet with Sharon and Israeli Foreign Minister Silvan Shalom, after meeting Qureia in Amman, Jordan, late Saturday. Burns is the first senior U.S. official to meet the sides since Qureia's new cabinet was sworn in earlier this month.

In another development, four key Palestinian negotiators of a symbolic peace agreement said they would not attend a signing ceremony in Switzerland on Monday after Palestinian leader Yasser Arafat refused to give written approval for the accord. Their absence threatened to undermine the unofficial deal, which enjoys significant support among Israelis and Palestinians.

Qureia issued his threat on Saturday, saying he sees no need to meet with Sharon if Israel does not show a willingness to compromise on the barrier and a host of other contentious issues.

"If they have an honest desire to seriously study these issues, the meeting will take place," Qureia said. "If the Israeli government says it will continue building the wall ... then there is no need for any meeting."

Israel says the barrier is necessary to block Palestinian homicide bombers. But Palestinians say the structure is an Israeli effort to seize their land. The barrier along the edge of the West Bank is expected to run more than 400 miles — with parts dipping deep into the West Bank.

Sharon has said he will not accept any preconditions for a meeting with Qureia.

In recent days, the Israeli prime minister has said he plans a series of "unilateral" steps if peace talks with the Palestinians fail. Media reports have said the moves could include the dismantlement of isolated Jewish settlements in the West Bank and Gaza.

On Sunday, Israeli security sources said the military chief, Lt. Gen. Moshe Yaalon, disagrees with Sharon's intention to take unilateral steps should peace talks fail. The army's "professional" opinion is that unilateral moves, such as dismantling settlements in the absence of a peace deal, will encourage terrorism, said the sources, who spoke on condition of anonymity.

Last month, Yaalon criticized Sharon for Israel's crackdown in the Palestinian areas, saying the harsh measures were encouraging, rather than deterring, Palestinian extremists.

Burns' trip to Jerusalem followed his meeting Saturday with Qureia in Amman. Burns is trying to revive the U.S.-backed "road map," which calls for a Palestinian state after violence has stopped. The plan has stalled amid continued fighting.

Qureia did not comment after the meeting. But Palestinian officials said beforehand that the prime minister would urge Burns to pressure Israel to halt construction of the barrier and to withdraw from Palestinian areas.

Qureia also was expected to tell Burns that he is optimistic about persuading Palestinian militants, in talks beginning Tuesday in Egypt, to halt attacks on Israel.

Qureia hopes to deliver a truce agreement to the Israeli government to pave the way for a cease-fire deal and renew talks with Israel on the road map. The Palestinian prime minister's criticism of Israel may have been aimed at gaining credibility with the militants ahead of the Cairo talks.

During Saturday's meeting, Burns repeated the U.S. commitment to establishing a Palestinian state, but said the Palestinians must end "terror and violence" against Israel, according to a statement issued by the U.S. Embassy in Amman, Jordan.

Burns also repeated President Bush's statement that Israel must "end the daily humiliation of the Palestinian people and rebuild trust," the statement said.