The Bush administration will be sending American Mideast mediator Gen. Anthony Zinni back to the Middle East this week to jump-start the stalled peace process between Israel and the Palestinian Authority.

Zinni, a retired Marine general, was abruptly called home in mid-December as violence and intransigence on both sides escalated during the three weeks of his visit.

The envoy's mission was not eased by Israeli Prime Minister Ariel Sharon's defeat of a plan by the Israeli president to declare a year-long ceasefire.

Zinni was to arrive in the area on Thursday and stay for four days, according to Paul Patin, spokesman for the U.S. Embassy in Tel Aviv. Patin added that Zinni would be asking Palestinian leader Yasser Arafat to dismantle militant and terrorist groups, and would ask Sharon to ease restrictions on Palestinians.

Palestinian negotiator Saeb Erekat said he expected Zinni to set a timetable for the various measures intended to restart the peace talks, steps detailed last year in a truce agreement negotiated by CIA chief George Tenet and in a series of recommendations by an international commission led by former U.S. Sen. George Mitchell.

Also on Tuesday, Israeli troops seized four suspected militants in two incursions into Palestinian territory.

There has been a significant drop in violence since Arafat renewed his call for a truce Dec. 16, following an especially bloody weekend of suicide bombings, and arrested scores of members of the militant Hamas and Islamic Jihad groups.

However, Israel's government has said Arafat needs to do more before it can talk about implementing the Mitchell recommendations, including a freeze in Israeli settlement construction in the West Bank and Gaza.

Sharon, meanwhile, blocked a proposal that Israeli President Moshe Katsav appear before the Palestinian parliament in the West Bank town of Ramallah and declare a yearlong truce with the Palestinians.

Sharon told Katsav that he strongly disapproves of the idea, said a senior Sharon aide, who spoke on condition of anonymity. Sharon suspects the proposal is a public relations ploy by Arafat, and that Katsav has been misled, the aide said.

Israel's Cabinet, responding to a spate of Palestinian attacks on Israeli civilians, last month declared Arafat "irrelevant" to Israel's fight against terrorism.

The idea of the Katsav speech was first raised by a former Israeli Arab legislator, Abdel Wahab Darawsheh, who referred to the truce to be declared as a "hudna," a term from Arab tribal law describing a specific period of non-belligerence. Darawsheh said the plan had Arafat's backing, and Katsav, a member of Sharon's right-wing Likud party, indicated he was interested.

The role of the Israeli president is largely ceremonial, and it is unusual for the president to get involved in policy-making. Katsav said Sunday he would not act without Sharon's blessing.

According to the Yediot Ahronot daily, Foreign Minister Shimon Peres, a member of the left-wing Labor party, also opposes the plan.

"We are trying to produce a cease-fire for generations, forever," Peres told the newspaper. "We want to end the cycle of terror and not just for a single year, as the president proposes."

Peres has been holding informal talks with Palestinian Parliament Speaker Ahmed Qureia on a framework for a possible peace deal. As a first step toward a treaty, before tackling the future of Jerusalem and the fate of Palestinian refugees, Israel would recognize a Palestinian state. However, the two sides remain far apart on the dimensions of such a state.

Also Tuesday, Palestinian security officials reported that Israeli tanks have pulled out of Nablus, one of several Palestinian cities where troops had taken up positions after a string of Palestinian attacks on Israeli civilians. The Israel military denied the report.

In another development, Israeli troops seized four suspected militants in two incursions into Palestinian territory, according to the army and Palestinian security sources.

The Palestinian leadership issued a statement saying the Israeli actions were part of an attempt to "put obstacles in front of Mr. Zinni."

The Associated Press contributed to this report.