The Palestinian Authority is set to demand that the Quartet pressure Israel to release prisoners in fulfillment of a pledge made by former Prime Minister Ehud Olmert to PA President Mahmoud Abbas, senior Palestinian sources told Haaretz on Monday.

Among the prisoners The PA wants released are Marwan Barghouti and Ahmad Saadat. The former is a member of the Fatah leadership, while Saadat is Secretary General of the Popular Front for the Liberation of Palestine (PFLP).

Abbas told Time Magazine a few days ago that, in 2008, Olmert promised him that Israel would release prisoners to the PA if a deal went through for the release of Gilad Shalit.

Olmert confirmed to Time that he had made the pledge.

Now the PA wants to present the demand ahead of a possible renewal of negotiations with Israel.

At the Knesset on Monday, MK Ahmed Tibi (United Arab List-Ta'al ) said that Israel should not be surprised if the two current conditions the Palestinians have set for restarting talks - a halt to construction in the settlements and recognition of the 1967 borders as a basis for negotiations - become three, the third being the prisoner release.

The PA's chief negotiator, Saeb Erekat, said on Monday that during meetings between Olmert and Abbas in Jerusalem in September 2008, as well as a few months later, Olmert pledged to release Palestinian prisoners if a prisoner swap for Shalit was concluded.

Erekat said a specific number of prisoners was not mentioned, nor were specific criteria, but that Olmert had agreed at the time that the number and criteria would be the same as those for prisoners released in exchange for Shalit, "and even better."

Erekat said this was not to be a condition for restarting negotiations, "just as the freezing of construction in the settlements is not a condition." Rather, it was a matter of fulfilling obligations, he said.

According to Israeli sources, Olmert had pledged to release 550 prisoners to Abbas so that a deal with Hamas would not increase its strength at the expense of the PA. However, the deal for Shalit includes 1,027 prisoners according to understandings with Hamas, and does not include gestures to Abbas by Israel.

The PA demand centers mainly on the release of some 170 longtime prisoners, who have been in Israeli jails since before the Oslo Accords.

Some members of the inner cabinet are said to support the Palestinian demand, but senior cabinet ministers have said over the past few days that the government does not intend to make any gestures to Abbas in light of his bid for statehood in the United Nations.

On Monday, Foreign Minister Avigdor Lieberman said that he vehemently opposed any such gesture, as did other inner cabinet members.

Lieberman also called for Mahmoud Abbas to resign, calling him the greatest obstacle to an agreement with the Palestinians. If Abbas would step down, negotiations might resume, Lieberman said.

On Monday, Palestinian leaders called Lieberman's remarks harsh incitement which constituted a call to harm Abbas. Also on Monday, Palestinian leaders spoke with senior American and European officials, protesting Lieberman's remarks.

Meanwhile, sources in Hamas said the head of the Hamas political bureau, Khaled Meshal, would be visiting the Jordanian capital, Amman, soon, together with a representative of the Qatari government.

Hamas representatives said the visit had been postponed for a few days, but that they believed two new Hamas bureaus would be opening soon, in Cairo and in Jordan. They also said a meeting might take place between Meshal and King Abdullah of Jordan.