Prime Minister Ariel Sharon said Monday he gambled and broke away from his hardline Likud Party because he did not want to squander peacemaking opportunities created by Israel's pullout from the Gaza Strip or waste time with political wrangling.

Sharon, whose split from Likud electrified Israeli politics and set the stage for likely March elections, ruled out unilateral withdrawals from the West Bank, however. He also said he remains committed to the internationally backed "road map" plan, which calls for a negotiated peace deal culminating in a Palestinian state.

"There is no additional disengagement plan," he told a televised news conference, referring to the summer's Gaza withdrawal. "There is the road map."

Sharon's decision to form a new party he described as "liberal" cemented his transformation from the hawkish patron of Israel's settler movement to a moderate peacemaker reconciled to the inevitability of a Palestinian state.

Weekend polls indicated Sharon, Israel's most popular politician, could marshal enough support to return to the prime minister's office for a third term at the head of a moderate coalition.

Palestinians said the developments created new prospects for peacemaking, which ground to a halt during five years of violence.

"I believe this is an eruption of an Israeli political volcano, and I hope that when the dust settles, we will have a partner in Israel to go toward ... a final arrangement," said Palestinian negotiator Saeb Erekat.

Sharon said he turned his back on former Likud allies who opposed his Gaza withdrawal because life within the party had become "insufferable."

"The Likud in its present configuration cannot lead the nation to its goals," said Sharon, the first sitting Israeli prime minister to quit his party.

The Gaza pullout created a "historic opportunity," he said. "I will not allow anyone to squander it."

Four small settlements in the northern West Bank were also evacuated along with Gaza, and Sharon said, as he has in the past, that additional West Bank settlements would be dismantled under a final peace deal.

But he reiterated that Israel would hold on to major settlement blocs in the West Bank where most of Israel's 235,000 settlers live, and demanded that Palestinians disarm militant groups.

Sharon set dramatic events in motion late Sunday with his decision to leave the party he co-founded more than 30 years ago with dreams of hanging onto the West Bank, Gaza Strip and east Jerusalem — lands captured in the 1967 Mideast war and claimed by the Palestinians for a state.

His decision to pull Israel out of Gaza touched off a bitter rebellion by former Likud allies. They failed to block the pullout, which enjoyed widespread support in Israel, but seeking revenge for Sharon's perceived treachery, continued going head-to-head with him in parliament.

On Monday, Sharon went to President Moshe Katsav to ask him to dissolve parliament, the Knesset, and move up elections to early March from their scheduled November date.

Katsav has yet to declare whether he would disband the legislature or let parliament dissolve itself — an option some lawmakers favor because that could buy them more time to campaign. While awaiting his decision, the Knesset voted Monday to disband, but needs to vote three more times to clear the way for early elections.

Sharon's push for March elections enjoys the support of Labor Party leader Amir Peretz, who heads Israel's second-largest faction in the Knesset.

Although Sharon has thrown off the constraints of Likud, peacemaking in the short term will be put on hold by Israel's elections and Jan. 25 balloting for the Palestinian parliament.

Efforts to jump-start peace moves after those votes could run into trouble if Hamas militants make a strong showing in the Palestinian balloting. Sharon has said he would not negotiate with a Palestinian government that includes Hamas.

Sharon's departure from Likud sets the stage for a turbulent election campaign, pitting him against a hawkish rump Likud and Peretz, a charismatic union leader who has rejuvenated the Labor Party with an appeal to previously alienated Jews of Middle Eastern ancestry.

Centrist political parties historically don't fare well in politically polarized Israel, and some said Sharon was taking a big gamble.

"He's always been a risk-taker," said Shmuel Sandler, a political studies professor at Bar-Ilan University. "He would have won the election (in a walk) if he had stayed in Likud, but he didn't stay because he felt they were going to put chains on him."

Still, Sandler said, neither Labor nor Likud would be able to attract enough support to cobble together a government. Sharon "will be the only one who can form a coalition," he said.

Labor, at Peretz's prodding, voted Sunday to pull out of Sharon's government, which it joined last year to ensure the Gaza pullout. Labor's withdrawal forced Sharon to make his decision now instead of closer to the originally scheduled November elections.

Peretz, a political dove who wants to increase social spending, has said he would consider teaming up with Sharon again under the right coalition lineup.

There was speculation that Labor veteran Shimon Peres would join with Sharon, but Peres didn't spell out his plans Monday.

Sharon wasn't considered likely to seek a coalition with Likud.

"Otherwise he would have stayed in the Likud Party and agreed to the opposition of the so-called rebels," said Avraham Brichta, a political science professor at the University of Haifa.

Likud's acting Likud chairman, Tzahi Hanegbi, said the party would elect a new leader quickly. The top contender is former Prime Minister Benjamin Netanyahu, who opposed the Gaza pullout.