CARIO, Egypt —Prime Minister Sharon’s bold gamble to leave the Likud party he helped create will leave his old party free to press for the retention of territory won in the 1967 Six-Day War, while paving the way for a likely Labor government when Israelis next vote for a parliament in the spring.

The realignment in Jerusalem following the dramatic announcement from Mr. Sharon on Sunday night has already prompted Mr. Sharon to ask for the dissolution of the Knesset and new elections for the legislative body expected to be held at the end of February or in early March.

The split in Likud has opened the door for the former prime minister, Benjamin Netanyahu, to lead a weakened Likud in opposition to any further unilateral repositioning of Israeli soldiers. Mr. Sharon has said that his new party, tentatively to be called “National Responsibility,” will adhere to an international plan known as the “road map” aimed at negotiating a Palestinian Arab state carved from the West Bank and Gaza. Meanwhile, Labor party leaders are expecting big gains this spring.

Mr. Netanyahu has led a revolt within Likud opposing the dramatic withdrawal of Israeli settlers and soldiers from Gaza. Last night, the Harvard-educated economist was already appealing to the defense minister, Shaul Mofaz, to stay in the Likud party and not defect to Mr. Sharon’s new one. In an interview with United Press International published on November 16, Mr. Netanyahu said he would only trade “peace for peace” with the Palestinian Arabs, and pointedly vowed to oppose any negotiations so long as Israeli citizens were under threat of terror attacks. Mr. Netanyahu agreed in 1998 for the CIA to train Yasser Arafat’s security organizations, a decision since criticized by his party for providing guns and know-how to agents that ended up cooperating with terrorists and not arresting them in 2000 at the start of the Intifadah.

“Likud will become a further right party, rather than right-center. If Bibi leads, it will exist for the first time as a neoconservative party that is strong on national security and supporting free markets,” a Middle East expert at the Hudson Institute, Meyrav Wurmser, said. “Likud will also likely shrink, it will be a major political expression for greater Israel even though they are likely to shrink.”

The Palestinian Authority’s chief negotiator, Saeb Erekat, said that the decision of Mr. Sharon to leave Likud was a “political volcano.”

“It is happening because of us, [the] Palestinian-Israeli conflict, and I have not seen anything more significant in Israel since 1967, when the occupation came to my home town [of] Jericho,” he said.

Meanwhile, Labor party member Yitzhag Herzog predicted that his party that is currently sharing power with Likud would emerge as an electoral victor in the next elections.

“The new development of the split in Likud will help us become perhaps the biggest party in the next election,” he said. “This development opens the way, opens the door, for a fascinating coalition of moderate forces after the election.”

Today, Israel’s president Moshe Katzav, said he would consider Mr. Sharon’s request to dissolve the Knesset. It is reported that Mr. Sharon will bring 14 out of the Likud Party’s 40 members in Knesset to his new party.