Jerusalem ? A much-anticipated summit between the Israeli and Palestinian leaders was suddenly thrown into doubt Sunday after Israel’s defense minister rejected key Palestinian demands during a preparatory meeting meant to ensure the upcoming session’s success.

Senior Israeli and Palestinian negotiators failed to bridge the differences Sunday, but they agreed to meet one last time in hopes of salvaging the summit.

The summit, tentatively set for Tuesday, would be the first between Israeli Prime Minister Ariel Sharon and Palestinian leader Mahmoud Abbas since Israel completed its withdrawal from the Gaza Strip last month.

The unilateral pullout has raised hopes that peace talks might soon resume. Israeli and Palestinian officials say they want to produce concrete results at a summit, hoping success would lead to formal negotiations toward a peace treaty.

But the two sides are deadlocked over several Palestinian demands, including the handover of West Bank towns to Palestinian security control and demands for more weapons for the embattled Palestinian security services.

Sharon told his Cabinet Sunday that he didn’t know if the meeting will take place, stressing that he will not threaten Israel’s security.

“There are gestures that Israel can and will make, and there are gestures that it won’t,” he said, according to meeting participants.

Abbas has said one of his goals will be to persuade Israel to carry out pledges it already has made, including pulling its troops out of five West Bank towns.

Israel agreed to the pullback as part of a February cease-fire. But the process stalled after two towns, Jericho and Tulkarem, were handed over, with Israel accusing the Palestinians of failing to take action against militants in those towns. Israel later retook Tulkarem after a suicide bomber from the area attacked an Israeli city.

Defense Minister Shaul Mofaz opposes any further handovers of Palestinian towns, the Defense Ministry said Sunday. Mofaz also objects to supplying Abbas’ security forces with new weapons.

The Palestinians say their security forces need better equipment to restore law and order in the chaotic Palestinian areas. Abbas has resisted international calls to disarm militant groups, fearing it would provoke civil war, though he recently banned armed groups from displaying weapons. The militants have repeatedly ignored the ban.

Mofaz’s decision raised doubts about the summit. Top Israeli and Palestinian officials met Sunday for what were expected to be final preparations for the summit.

After the meeting, Palestinian negotiator Saeb Erekat said the two sides would decide Monday whether to hold the summit the following day.

The two sides have made progress on other Palestinian demands in recent days, with Israel showing flexibility on the release of some of the more than 7,000 Palestinian prisoners it holds and a possible compromise on reopening Gaza’s border with Egypt.

Israel closed the Rafah terminal – the main exit out of Gaza – before the withdrawal. The Palestinians say reopening the border is essential for Gaza’s ravaged economy.

Abbas is to travel to Washington later this month to meet with President Bush, and he would be reluctant to arrive without any concrete achievements from a meeting with Sharon.

In other developments:

l Israel reopened a cargo crossing on its border with Gaza on Sunday, and Palestinians said this would alleviate a shortage of fruit and dairy products in the territory. The Karni passage and others within the Palestinian area had been closed almost continuously since Sept. 24 after dozens of rockets were fired from Gaza into Israel.

l Abbas and Palestinian Prime Minister Ahmed Qureia are to attend a gathering in memory of slain Israeli Prime Minister Yitzhak Rabin, organizers said Sunday. They said the two would address a conference in the seaside city of Netanya in early November, when Israel marks 10 years since Rabin was gunned down by an extremist Israeli opponent of his policy of compromise for peace with the Palestinians.

l A Palestinian militant was killed in a clash with Israeli troops in the northern West Bank, the army and Palestinians said. A militant group affiliated with the ruling Fatah Party said three of its men tried to attack troops, and one was killed in a shootout.