The Israeli government on Sunday approved the release of 90 Palestinian prisoners, its latest gesture meant to bolster Palestinian President Mahmoud Abbas in his power struggle against the militant Islamic Hamas.

But Palestinians reacted with disappointment, urging Israel to free larger numbers of prisoners at a time when the sides are trying to step up peace efforts.

An Israeli government spokeswoman said the prisoners could be freed as early as Tuesday evening. Prime Minister Ehud Olmert proposed the current release — timed to coincide with Ramadan, the Muslim holy month — in his last meeting with Abbas two weeks ago.

The meetings are intended to forge guidelines for a U.S.-sponsored peace conference tentatively scheduled for Washington in November. Palestinians are pressing for a detailed document, while Israel wants a vaguer text.

Israel is holding about 11,000 Palestinians. Demanding their freedom has become a keystone in Palestinian politics, as many families have a relative in an Israeli prison. Top on the list for Palestinians are the ones the Israelis are least likely to let go — uprising leaders convicted of involvement in attacks against Israelis.

The Israelis say the 90 have more than a year to run on their sentences, but none were directly involved in fatal attacks.

The Palestinians to be freed at members of Abbas' Fatah movement or its allies — not from Hamas, which overran Gaza in June and is in a crucial power struggle with the more moderate Fatah.

One-third of the prisoners are from Gaza, according to a statement from the Prime Minister's office after a committee approved the list. Olmert spokeswoman Miri Eisin said. Israelis would then have 48 hours to challenge their release in the Supreme Court.

"In theory, Tuesday night or Wednesday morning, you can release the prisoners," she said. The statement said the release would be in coordination with Abbas' office.

The last prisoner release as in July, when 250 were freed.

In the past, freed prisoners have been greeted emotionally by their families, and then many denounce Israel for holding the other prisoners and demand their freedom — erasing much of the good will the Israelis were seeking, as well as the credit Palestinian moderates were hoping to garner with the release.

Abbas emphasized the importance of the prisoners to Palestinians.

"The prisoner issue is at the crux of the peace process, and there can't be an agreement while thousands of prisoners are in Israeli jails," he said Sunday.

The Palestinians have long demanded that prisoner releases be coordinated with the Palestinians through negotiations.

"If there was a large release of prisoners, it would support the Palestinian president and government, but when Israel makes unilateral moves it does not do much to support President Abu Mazen (Abbas) and the legitimate government," said Ashraf Ajrami, the Palestinian minister for prisoner affairs.

"What Israel is doing is ignoring Palestinian demands," Ajrami said.

In Gaza, Hamas accused Fatah of working hand in hand with Israel.

"The 100 Palestinian prisoners are from Fatah, and that means continuing discrimination against prisoners, with Fatah's agreement," said Hamas spokesman Sami Abu Zuhri. "It's dangerous...when the occupation (Israel) and Fatah play the same role in discriminating against the prisoners."

Hamas is sworn to Israel's destruction and has carried out dozens of suicide bombings that have killed more than 250 Israelis.

Six of the 22 Israeli Cabinet ministers voted against the release, including ex-Defense Minister Shaul Mofaz from Olmert's Kadima Party. They said that such gestures are ineffective and possibly dangerous. Almagor, a group representing relatives of victims of Palestinian attacks, counts 179 civilians, mostly Israelis, killed by Palestinians who were released in deals and gestures since 2000.