Jerusalem ? Israel threatened Sunday to invade Gaza if Palestinian leader Mahmoud Abbas does not control militants who have stepped up rocket and mortar attacks ahead of Israel’s planned pullout from the coastal strip next month.

Abbas pledged to do his utmost to stop the barrages but warned that an invasion of Gaza would “sabotage everything.”

Prime Minister Ariel Sharon said all restraints are off and thousands of Israeli troops have massed along the Gaza border. The sudden escalation is the most serious threat yet to a 5-month-old truce that had drastically reduced Palestinian-Israeli violence after more than four years of bloodshed.

More than 100 rockets and mortars have rained down on Gaza settlements and Israeli villages just outside the territory in the last four days. Hamas leaders say they are retaliating for Israeli violations of the truce.

But one leader said the main reason for the barrage was to show that Israeli settlers were fleeing Gaza under fire rather than in a planned evacuation.

Soldiers and tanks were poised to cross the Gaza border fence. Large-scale raids often have followed rocket and mortar barrages but not since the truce took effect Feb. 8.

Sharon told his ministers at a weekly Cabinet meeting: “I spoke to the heads of the defense establishment … and informed them that there are to be no restraints on our operations.”

Despite the tough talk, there were signs both sides want to maintain the truce. “We are going to do our utmost to stop these rockets,” Abbas told a news conference in Gaza. “I cannot promise how much time it will take me.”