JERUSALEM -- A small ultra-Orthodox political party agreed yesterday to join Israel's ruling coalition, paving the way for Prime Minister Ariel Sharon to form a new government and push ahead with plans to uproot the Jewish settlements in the Gaza Strip.

At the same time, the Israeli leader issued his toughest warning yet to settlers and their supporters who are threatening to physically resist the evacuation of the communities.

"Whoever raises his hand to a soldier or a police officer or a member of the security forces, or whoever organizes refusal [of army orders], whoever makes threats -- we will move against him with all our might," said the prime minister, addressing a group of Israeli soldiers.

Earlier in the week, these same troops arrived to dismantle an illegal settlement outpost of Yitzhar in the northern West Bank and found themselves caught up in an ugly clash with young settlers.

Although no one was seriously injured in Monday's melee, Israelis collectively shuddered at the sight of young soldiers being spat at and cursed by furious settlers. In a country where military service is mandatory for almost everyone, the army is a highly respected institution and one with which most citizens closely identify.

Unease over the incident was magnified by the fact that an off-duty soldier from Yitzhar donned his uniform, rushed to the scene and urged the troops to disobey orders to dismantle the outpost. The soldier, Sgt. Yosef Filant, was swiftly court-martialed and sentenced yesterday to 28 days in the stockade for conduct unbecoming a soldier, Israeli media reported.

Sharon plans to evacuate all 21 Jewish settlements in Gaza and four smaller communities in the West Bank later this year.

Sharon's Gaza pullout plan received a major boost with yesterday's agreement in principle by the United Torah Judaism party to join his government. He already had secured an agreement with the left-leaning Labor Party to form an alliance, but that would have given him only a bare majority in the 120-member Knesset. With United Torah Judaism in the fold, his coalition will control 66 seats.

Formal agreements on the parties' alliance were expected to be signed today, and the new government sworn in early next week.

United Torah Judaism accepted Sharon's overture on the advice of its spiritual leader, an eminent rabbi, but agreed only to stay in the government for a three-month trial period.

The party's main interest is in safeguarding funding in the upcoming national budget for its ultra-Orthodox constituency.