American Middle East envoys hold separate talks Thursday, with Israeli Prime Minister Ariel Sharon and his Palestinian counterpart, Ahmed Qureia. At issue are the Israeli leader's plans for unilateral disengagement from the Palestinians and overall prospects for resuming peace efforts.

Assistant Secretary of State William Burns and National Security Council advisers, Elliott Abrams and Stephen Hadley are on their third trip to the region for what U.S. officials describe only as an ongoing diplomatic effort.

During their one-day visit, the envoys meet with Israeli Prime Minister Ariel Sharon to try to pin down details of his proposed disengagement plan. They also hold talks with Palestinian Prime Minister Ahmed Qureia in the West Bank town of Jericho.

Prime Minister Sharon is promoting his plan to withdraw Israeli troops and settlers from most, if not all, of the Gaza Strip and to disband several Jewish settlements in the West Bank. He says Israel must take this unilateral step to disengage from the Palestinians because peace talks with the other side are simply going nowhere. Addressing a technology conference in Tel Aviv Wednesday, he said the current situation cannot continue. He warned that if Israel does not disengage, it could spell disaster.

The Palestinians are wary of the Israeli plan, fearing that any unilateral action will allow Israel to establish new facts on the ground that could preclude the independent state the Palestinians want in the future.

Prime Minister Qureia was careful Wednesday in his lukewarm endorsement of the disengagement plan. He said the Israeli withdrawal would be welcome if it entailed a complete pullout from Gaza as a first step toward resuming broader peace negotiations.

The U.S. diplomats will want as many details as possible from Mr. Sharon about his withdrawal plan - before the Israeli leader meets to discuss it with President Bush in Washington later this month.

Israeli officials are quoted as saying that the talks are also about what Israel will get in return for the pullout. Israel is reportedly seeking a number guarantees from Washington - including concessions concerning the eventual right of return of Palestinian refugees, future borders and inclusion into Israel of large Jewish settlement blocs in the West Bank.

These are all contentious issues that are supposed to be worked out in a final status agreement between Israel and the Palestinians. Even perceived concessions beforehand would likely only heighten Palestinian suspicions that Mr. Sharon's limited disengagement is in fact the final settlement he wants to impose.