Israel will free 400 Palestinian prisoners on Thursday in what Prime Minister Ariel Sharon has called an attempt to boost moderate Palestinian Authority Chairman Mahmoud Abbas ahead of a Gaza withdrawal.

The Israel Defense Forces said on Wednesday the mass release, to be carried out in cooperation with the Israel Prison Service and the PA, stemmed from approval granted earlier this week by the cabinet and reflected "ongoing cooperation with the Palestinian Authority."

The prisoners, residents of the West Bank and the Gaza Strip, will include some members of the Islamic movements but the majority will be Fatah activists. The list of prisoners slated for release was compiled by a committee headed by Justice Ministry Director General Aharon Abramovitz together with representatives from the police, Israel Defense Forces, Prisons Service and the Shin Bet.

None of the prisoners slated for release on Thursday had been convicted of attacks that killed or wounded Israelis, officials said.

Palestinians have dismissed the long-delayed release as a public relations stunt, complaining that Israel refused to give them a say in who would be freed, and prisoners they most wanted released would stay in jail.

Israel freed 500 prisoners in February after Abbas and Sharon announced a cease-fire, but Sharon later suspended the promised release of 400 more, saying Palestinians had not done enough to disarm militants.

Sharon has said he wants to bolster Abbas ahead of a pullout from all 21 Jewish settlements in Gaza and four of 120 in the West Bank that is slated to begin in August as part of Sharon's plan to "disengage" from conflict with the Palestinians.

Israel is hoping that Abbas, elected to succeed Yasser Arafat on a platform of non-violence, will keep militants from carrying out attacks during the pullout. Abbas coaxed militants into the shaky truce he agreed with Sharon.

The Legal Institute for Terror Research filed a petition with the High Court of Justice on Wednesday against the prisoner release. The petitioners argued that releasing the prisoners and transferring them to the territories would not help strengthen Abbas' standing.

Hamas, sworn to Israel's destruction and the biggest rival to Abbas' ruling Fatah party, has said continuing the truce is partly contingent on prisoner releases. About 8,000 Palestinians are held in Israeli jails.