Israeli Foreign Minister Shimon Peres postponed a planned Saturday meeting with a Palestinian delegation, slowing the pace of recent contacts between the two sides.

The official reason given for postponing the meeting is that more preparatory work needs to be done to ensure that, as the foreign minister's office put it, the talks can succeed.

But Israeli media reports say the real reason is objections from Prime Minister Ariel Sharon. They said Mr. Sharon is worried that too many talks with officials from the Palestinian Authority could undermine his efforts to oust Yasser Arafat. He has said any contacts between Israeli and Palestinian officials should deal only with humanitarian issues.

Earlier this week, Mr. Peres held the first cabinet-level talks in months with the Palestinians, meeting new Finance Minister Salam Fayad on Monday and new Interior Minister Abdelrazek al-Yahya on Tuesday.

Both Palestinian officials were to have taken part in Saturday's meeting.

Secretary of State Colin Powell, meanwhile, said a letter from Yasser Arafat about efforts to reform the Palestinian Authority does not affect his decision not to deal with the Palestinian leader.

Mr. Powell said Friday that his office will consider the letter, but that the Bush administration stands by its decision to wait for new Palestinian leadership to emerge.

Mr. Arafat's letter follows demands by President Bush to reform the Palestinian Authority and for the Palestinian leader himself to step aside. Since then there has been no senior-level U.S. contact with Mr. Arafat.

Elsewhere, the Israeli army said it safely detonated a car packed with explosive that the military said was headed toward Israel.

The vehicle, which was stopped near the northern West Bank town of Qalqilya was found to be carrying four explosive devices connected to gas canisters that were wrapped in nails.

Israeli forces said they have intercepted three car bombs and arrested 15 would-be Palestinian suicide bombers since they re-occupied nearly all the West Bank three weeks ago.