Two top U.S. officials were scheduled to arrive in Israel Wednesday to begin preliminary negotiations ahead of next week's diplomatic summit in Washington, the first direct Israeli-Palestinian talks in 20 months.

The two officials are Daniel Shapiro, a top National Security Council staffer handling Israel and neighboring countries, and David Hale, deputy to special Mideast envoy George Mitchell.

Each official will meet separately with Isaac Molho - an adviser to Prime Minister Benjamin Netanyahu and head of the Israeli negotiating team - and chief Palestinian negotiator Saeb Erekat.

Sources close to Netanyahu said the Palestinians are pressuring the Americans to hold the tripartite meeting with Molho and Erekat in Jerusalem either tomorrow or the next day as part of efforts to lay the groundwork for the Washington summit. Netanyahu and Molho are reportedly cool to the idea, but U.S. officials are said to be supportive of the Palestinian offer.

"It's possible a trilateral summit will ultimately be held," a top-ranking U.S. official told Haaretz Tuesday.

If the meeting goes ahead, the Palestinians are expected to raise almost immediately the issue of Israel's settlement construction freeze, due to expire in Spetember. Israeli and U.S. negotiators are reportedly interested in addressing that issue only after the start of the Washington summit.

Mitchell has reportedly told both Netanyahu and Abbas that the Obama administration expects that after the start of direct talks, both sides will refrain from taking any steps to compromise the progress of negotiations.

A senior U.S. official involved in contacts with Israel declined to comment over whether the U.S. has issued a clear message to Jerusalem over the future of settlement building.

"Our position on the matter of settlements is known and hasn't changed. We believe that building in the settlements is illegitimate," he said.

"We've made it known to both sides that once negotiations begin we expect that efforts will be made to advance talks and not hinder them. We intend to do everything possible so that the talks don't fail once negotiations begin."