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National Security Adviser Condoleezza Rice (search) and Palestinian Prime Minister Mahmoud Abbas (search) discussed the Mideast peace plan Saturday in a meeting that included an invitation to visit Washington in the coming days. The talks preceded by a day an expected truce declaration by Palestinian militants.

Abbas accepted the invitation, which includes a meeting with President Bush, a senior Palestinian official said. The White House was not able to confirm the invitation.

Hoping to advance a U.S.-backed peace plan, Rice spoke with Abbas (search) for four hours in a plush hotel in the West Bank city of Jericho. The Palestinian leader pressed demands for the release of political prisoners held by Israel, a full withdrawal of Israeli troops from Palestinian territories and a freeze on Jewish settlement activity there, Palestinian Cabinet Minister Yasser Abed Rabbo said.

"The meeting was very positive," he said, with American officials showing an "understanding" for Palestinian demands.

On Sunday Rice will meet with Israeli Prime Minister Ariel Sharon (search), the same day militant groups are planning to announce formally that they will begin a three-month freeze on attacks against Israelis. Some militants, however, suggested the truce announcement might be pushed a day later.

A truce, coupled with a preliminary agreement by Israel to withdraw troops from the Gaza Strip and Bethlehem, could provide a major boost to the "road map" peace plan introduced by President Bush at a June 4 Mideast summit. The plan is a blueprint to end 33 months of bloodshed and create a Palestinian state by 2005.

Still, the potential for violence loomed. At least one vehicle in a convoy of U.S. diplomatic cars traveling in Gaza suffered damage after two explosive devices blew up, Israel's military said. No injuries were reported and U.S. embassy officials refused to comment or give more details.

The Syrian-based leaders of the two main Islamic groups, Islamic Jihad and the larger Hamas group, agreed to a truce earlier in the week, according to a Palestinian legislator involved in the negotiations. But Gaza-based militants initially denied there was a deal, then said details remained to be worked out.

"We have accepted a conditional cease-fire for three months," Mohammed al-Hindi, an Islamic Jihad (search) leader in Gaza, told The Associated Press on Saturday, in the first on-the-record confirmation of the truce from a militant leader.

Ramadan Shalah, the main Islamic Jihad leader based in Damascus, told the Dubai-based Al Arabiya satellite channel that Islamic Jihad "has agreed with the Hamas (search) movement and the Fatah movement to suspend military operations" against Israel. He said he expected an announcement Sunday.

Hamas leaders also have said they agreed to a truce but will only formally declare their acceptance in a joint document still being finalized.

The truce applies to the West Bank and Gaza, as well as Israel, fulfilling a key Israeli demand.

A formal announcement was expected Sunday, but Al-Hindi said it could be put off until Monday, if necessary.

Intensive meetings continued Saturday among Islamic Jihad, Hamas and Palestinian leader Yasser Arafat's (search) Fatah faction to work out the final wording of the truce announcement.

There also were efforts to convince 10 smaller factions to join the truce. At least one of them, the radical Popular Front for the Liberation of Palestine (search), appeared to be holding out approval, a Palestinian negotiator said on condition of anonymity.

A number of West Bank leaders, speaking in the name of the Al Aqsa Martyrs' Brigades (search), also complained in a statement that they had not been consulted on the deal. The Brigades are loosely linked to Fatah.

It remains to be seen whether all militants will comply with a truce announcement. The Al Aqsa Martyrs' Brigades in particular are thought to be difficult to control, since they are composed of many rebellious armed gangs scattered throughout the West Bank.

Israel and the United States also have given the emerging truce a lukewarm response, saying the road map requires armed groups to be dismantled. Fearing a crackdown could trigger a civil war, Palestinian officials have opted instead for persuasion.

The White House welcomed a preliminary agreement Friday to turn over security responsibility in Gaza and Bethlehem to the Palestinian Authority, calling it a "first significant joint step toward implementation of commitments" Israeli and Palestinian leaders made at the summit with Bush.

The road map requires that Israeli forces gradually withdraw to positions held before the outbreak of fighting in September 2000.

Israel was "cautiously optimistic" about the pullback arrangements, Foreign Ministry Spokesman Yonatan Peled said Saturday, but expected the Palestinian Authority to "keep a lid on terrorist activity emanating from the Gaza Strip."

The deal, reached in talks between Palestinian security chief Mohammed Dahlan and Israel's Maj. Gen. Amos Gilad, came with a pledge by Israel to halt targeted killings of wanted Palestinians — one of the militants' key demands for continuing with a truce.

Palestinians in turn agreed to act against what Israel calls "ticking bombs" — assailants on their way to attack Israelis. But Peled said Israel reserved the right to go after assailants themselves if Palestinians failed to do so.

Arafat's Fatah approved the deal at its weekly Saturday meeting. Details of how to implement it were to be worked out at meetings Sunday in Gaza and Bethlehem.

The progress in negotiations was accompanied by increasing pressure by Palestinians for guarantees on Israel’s freeing of jailed Palestinians.

A crowd gathered outside of Abbas' office Saturday in the West Bank town of Ramallah, noisily demanding he raise the issue with Rice.

Entering the crowd, Abbas got his hands on a loudspeaker and shouted: "There will be no peace or security if even one Palestinian prisoner remains behind bars. Be sure that we will exert our utmost in order to empty all prisons of prisoners."

Peled said Israel already has released some prisoners as a good-will gesture and was "definitely willing" to release more, "but only after we see some steps, some action, some responsibility" taken by Abbas.

Rice planned to continue talks with Palestinian officials on Sunday, while lower-level U.S., Israeli and Palestinian officials held separate trilateral meetings.

She was due to meet Sunday with Sharon and, separately, with Foreign Minister Silvan Shalom and Defense Minister Shaul Mofaz.

The Associated Press contributed to this report.