Jerusalem ? Prime Minister Ariel Sharon declared himself unbowed Monday by his party’s crushing rebuff of a U.S.-endorsed plan to withdraw Israeli soldiers and settlers from the Gaza Strip.

“I want to say in the clearest fashion: I will come up with another plan,” the 76-year-old prime minister told lawmakers from his conservative Likud Party, which a day earlier had rejected his pullout initiative by an overwhelming 3-2 margin.

“I will come up with a plan that will get broader support,” Sharon pledged, according to those present in the closed-door meeting.

The prime minister also said he would bring his new proposal, the outlines of which were not disclosed, to his divided Cabinet and to the Israeli parliament, or Knesset, for approval.

Jewish settlers and their supporters mounted a highly effective grass-roots campaign against Sharon’s plan, defeating it by a much larger than forecast margin.

The vote was overshadowed — and perhaps influenced — by the death of a pregnant Gaza settler and her four young children in a shooting attack by Palestinian gunmen while the polling was taking place.

Sharon and his allies said the success or failure of his initiative to withdraw from Gaza could not rest only with registered Likud members, only half of whom — fewer than 100,000 people — turned out for the vote.

Sixty percent of the those voting rejected Sharon’s plan; about 40 percent were in favor. Those voting in the referendum made up only about 1 percent of the Israeli public.

Palestinians, who were somewhat bemused to find themselves in Sharon’s corner during the campaign — albeit quietly — described the Likud balloting as an internal Israeli affair. Some officials, though, were dismayed to see the withdrawal initiative voted down.

Palestinians had said that any Israeli pullout from Palestinian territory was a positive development, although many were worried that Sharon intended to use the Gaza withdrawal as a pretext for seizing large swaths of the West Bank.

“It is very strange when … so few people decide the fate of Israel, the peace process and relations between Israelis and Palestinians,” said Palestinian lawmaker Ziyyad Abu Ziyyad. “I believe the right step should be to return to the negotiating table.”

In other developments:

l An Israeli attack helicopter fired a missile early today at a group of armed Palestinians in a Gaza refugee camp, killing two and wounding at least 17, residents and doctors said.

Residents who saw the Khan Younis refugee camp violence said the gunmen first fired missiles at Israeli tanks before the helicopter opened fire.

l Israeli troops today took up positions around Palestinian leader Yasser Arafat’s office building in the West Bank city of Ramallah. Witnesses said Israeli military vehicles surrounded the complex and soldiers took over buildings across from the compound.

Israeli military officials said soldiers were arresting suspects, but the operation was not linked to Arafat’s office.