Jerusalem ? The Likud Party on Sunday soundly rejected Israeli Prime Minister Ariel Sharon’s proposal to unilaterally withdraw from the Gaza Strip in a lopsided vote that took place after a pregnant settler and her four children died in a shooting attack by Palestinian gunmen.

Early returns and exit polls by three Israeli media outlets showed significant opposition to the proposal, which calls for evacuating all 21 settlements in the Gaza Strip and four others in the northern West Bank. Under the plan, Israel would keep settlements in the West Bank but would turn over the Gaza Strip to the Palestinians.

The results of voting by Likud’s rank and file threw into question Sharon’s political future and dealt a setback to Bush administration efforts to cast its embrace of the plan as a way to revive the U.S.-backed “roadmap” to peace.

Sharon said he would not resign, but he conceded that he had lost the referendum that he allowed to build support for his plan.

“There are many who are as disappointed as I am with the results,” Sharon said in a written statement issued late Sunday. “The coming days will not be easy. I will consult with the Cabinet ministers over the coming days and will carefully examine the implications and the steps we’ll take.”

But, he added, “One thing is clear to me: the people of Israel did not elect me to sit with my hands folded in my lap for four years. I was elected to find the way to bring the calm, the security and the peace the people deserve.”

Before the voting, Sharon suggested he would seek government approval for the plan even if Likud rejected it. Sharon originally said he would abide by the referendum of Likud’s nearly 200,000 voting-eligible members, but later asserted that the internal vote was not legally binding.

Suspense over the outcome was punctuated by the midday ambush, which took place on a road leading to the Gush Katif bloc and seemed to provide fodder for both sides of the debate about the pullout proposal. The family reportedly was on its way to Israel, where they were going to distribute fliers urging Likud members to vote against Sharon’s plan.

A joint claim of responsibility for the shooting came from the militant wings of two Palestinian organizations, Islamic Jihad and the Popular Resistance Committees, an umbrella group. They said the attack was retribution for Israel’s assassination of the last two leaders of Hamas, the militant group responsible for dozens of suicide bombings and other attacks on Israelis.

Relatives and friends of 34-year-old Jewish settler Tali Hatuel and her four daughters, aged 2 to 11, attend their funeral Sunday at a cemetery in the southern Israel town of Ashkelon. Palestinian gunmen shot and killed the pregnant woman and her four children near the settlement where they lived in the Gaza Strip.

Hamas founder Sheik Ahmed Yassin was killed in an Israeli airstrike in March and his successor, Abdulaziz Rantisi, died in a similar missile strike less than a month later.

Several hours after the shooting, an Israeli gunship fired missiles into a Gaza City building housing a radio station. The Israeli military said the station had aired interviews with senior Hamas leaders that incited attacks and had broadcast warnings about the movements of Israeli soldiers.

The defeat of Sharon’s plan came at the hands of an energetic opposition organized by the Gush Katif settlers and thousands of their right-wing supporters.