Israeli Prime Minister Ariel Sharon fired two members of his cabinet on Friday, gaining the cabinet majority needed to pass his Gaza Strip withdrawal plan but placing the future of his coalition government in doubt.

Sharon sent a messenger to deliver notices of dismissal to two nationalist members of the National Union party, Transportation Minister Avigdor Lieberman and Tourism Minister Benny Elon, after they failed to answer his summons to a meeting Friday morning.

Members of Sharon's coalition said the dismissals would help the prime minister avoid either a defeat of the measure in a cabinet vote on Sunday or adoption by the cabinet of a toothless version of the plan.

"I didn't ignore the attempts to reach a compromise, but there were some things I couldn't give in to and I didn't," Sharon told the Israeli newspaper Haaretz. "I need a majority on Sunday."

The cabinet is to vote on Sharon's proposal to evacuate, by the end of 2005, the 21 Jewish settlements in Gaza along with four West Bank settlements. The cabinet is then expected to vote on the first of four phases of the plan, the evacuation of three Gaza settlements. Each following phase of the withdrawal would be voted on in turn.

"We can't freeze the plan any longer," said a source in the prime minister's office. "We don't have a partner, but the world is not going to accept us staying still and not doing anything."

But Friday's dismissals also threw the future of Sharon and his government -- and future stages of any evacuation plan -- into question.

Sharon's coalition controls 68 of 120 seats in parliament. But with the firing of its two leaders in Sharon's cabinet, the National Union party, which holds seven seats, plans to leave the coalition, according to members.

"We will do whatever we can to make it impossible to go on with his terrible program," said Yuri Stern, chairman of the party's faction in the parliament, or Knesset.

Without the National Union, Sharon's coalition would depend for its survival on another small, pro-settler faction, the National Religious Party, whose six members are also threatening to bolt.

"I don't like the price and it won't bring peace," said Nisan Slomiansky, chairman of the National Religious Party faction in the Knesset, who said he hopes his party will abandon the government.

Shas, an Orthodox Jewish party whose chairman phoned members of the National Union to bless them, according to reports in the Israeli press, has called for a no-confidence vote on Monday.

Abraham Diskin, a Hebrew University expert on Sharon's Likud Party, said the prime minister is likely to try to form a new governing coalition with the Labor Party, and that Labor, despite internal divisions, seems amenable.

In addition, Sharon's proposal faces opposition within his party. Likud has supported settlement construction in Gaza and the West Bank for decades, and party members defeated Sharon's pullout plan in a referendum May 2.

Finance Minister Binyamin Netanyahu, a Likud leader and former prime minister, opposes it on the grounds that the party has rejected it, said an aide. Netanyahu's goal is to abide by the Likud members' decision, not "to topple Sharon or to form a different government," the aide said.

But that "could be the outcome," he said.

"There are so many open possibilities, it's hard to predict what will happen," said Deputy Prime Minister Yosef Lapid, a member of the Shinui party who supports withdrawal from Gaza.

Lapid and other members of Sharon's cabinet expressed relief at the dismissal of two of the most right-wing members of the government.

"We shouldn't sit with these kinds of people anyway," Lapid said, noting that Elon and Lieberman are proponents of deporting Palestinians from East Jerusalem and the West Bank and Gaza. Lapid said he hoped a centrist base could be formed in a coalition of Likud, Shinui and Labor.

A messenger spent Friday morning chasing the two ministers, who were trying to avoid receiving the notices of their dismissal, which would take effect only 48 hours after receipt. They hoped that this hide-and-seek would allow them to vote in the cabinet meeting Sunday morning. Lieberman was finally handed his notice while on a treadmill at a gym, said his spokesman, Shai Rosenfeld. Elon had not yet received the message by Friday evening, an aide said.

Lieberman told Israel Radio he was "proud" to have been fired for standing up for his beliefs. "I joined this coalition on the basis of principles which we agreed to," he said. "There is no connection between these principles and the disengagement plan."

Researcher Samuel Sockol contributed to this report.

Transportation Minister Avigdor Lieberman of the National Union party was handed his dismissal notice while at a gym. Tourism Minister Benny Elon, shown in April, also failed to answer summons to a meeting called by Prime Minister Ariel Sharon.