Prime Minister Ariel Sharon (search) on Tuesday warned Jewish settlers opposed to his plan to withdraw from the Gaza Strip (search) that the use of violence against security forces constitutes a threat to Israel's existence.

Sharon spoke as the Israeli army opened disciplinary proceedings against a U.S.-born soldier who refused orders to help demolish 11 abandoned homes in a seaside Gaza settlement. During Sunday's operation in the Shirat Hayam settlement, young settlers pushed soldiers, cursed and blocked bulldozers — giving them a taste of what could lie ahead.

Sharon said settlers who use violence are a minority among the 9,000 Israelis slated for evacuation from their homes in the Gaza Strip and four small West Bank (search) settlements.

"I especially warn against attempts — by a small lawless, minority ... using violence against the army and other security forces," Sharon said at an annual conference for the quasi-governmental Jewish Agency.

He also condemned calls for soldiers to disobey orders to carry out the evacuations, set to begin in August. "We all have to remember that the calls to refuse and to disrupt life in Israel endanger the existence of Israel as a Jewish, democratic state," he said.

Defying Sharon's sharp words, a group of settler rabbis repeated their call for soldiers to refuse orders to evacuate settlers, issuing a statement that calls the Gaza withdrawal "immoral."

Jewish settlers gathered outside military headquarters in Gaza to protest the arrest of Cpl. Avi Bieber for refusing to participate in the demolitions. Bieber faced a disciplinary hearing Tuesday. It was unclear whether the court would make a ruling in the closed-door hearing.

One of the demonstrators, militant settler Itamar Ben-Gvir, was detained for questioning, Israeli police said. Ben-Gvir is a member of the outlawed Kach group.

Ben-Gvir and dozens of other hard-liners recently took over a seaside hotel in the Gaza settlement of Neve Dekalim (search), where they vow to resist the evacuation to the end. They have stockpiled food and water and surrounded the abandoned hotel with barbed wire to keep out security forces.

At Shirat Hayam, Jewish settlers have already set up a new outpost aimed at re-establishing their presence in the area. On Tuesday, settlers clashed with Palestinians at the site. One Israeli girl was lightly wounded by a rock thrown by a Palestinian.

Meanwhile, in the Palestinian refugee camp of Khan Younis (search) — adjacent to Neve Dekalim — Palestinian security forces sealed the entrance of an underground tunnel leading from the camp to the Israeli community.

The Israeli army, which informed Palestinians of the tunnel, said Islamic militants had planned to use it to attack the settlement. The army destroyed the section of the tunnel inside the settlement on Monday.