JERUSALEM (AP) – Palestinian-Israeli fighting spilled over into a third straight day Friday with a coordinated attack by three militant groups on a Jewish settlement in the Gaza Strip. One Palestinian was killed during a shootout with troops.

Israel warned that a cease-fire declared in February is in danger of collapse and threatened to retaliate if Palestinian leader Mahmoud Abbas fails to rein in militants. Abbas, visiting India on Friday, said he was hopeful the truce would stick.

A flare-up in fighting could complicate Israel’s plans to withdraw from Gaza this summer. But Asaf Shariv, Prime Minister Ariel Sharon’s spokesman, said Israel would push ahead with the pullout no matter what.

In Friday’s attack, three militants fired missiles, mortars and assault rifles at the Gaza settlement of Kfar Darom, the army said. Hamas said it carried out the attack with the Popular Resistance Committees, a Gaza militant group, and the Al Aqsa Martyrs’ Brigades, a violent group with ties to Abbas’ ruling Fatah party.

One militant was killed in an ensuing gun battle, and two others escaped, Hamas and the army said. Hamas said the attack was in retaliation for Israeli strikes.

The fighting has erupted while Abbas is on a two-week tour of South America and Asia, prompting Israeli criticism not only of the violence but also of his lengthy absence. Abbas also is heading to the United States next week to meet with President Bush.

The ongoing violence “only shows that their leader has to be in the area and not disappear for 20 days,” Shariv said. He said Israel sent “very strong messages” that the cease-fire is in danger and “if the Palestinians don’t stop the firing then we will have to do it.”

In any case, Shariv said Israel will go ahead with plans to withdraw in August from all settlements in the Gaza Strip and four in the West Bank.

“The pullout is for Israel. It has nothing to do with the Palestinians,” Shariv said. “If during the pullout there will be Palestinian fire, our response will be harsher then ever.”

Sharon announced his Gaza withdrawal plan last year as a unilateral Israeli withdrawal. However, after Yasser Arafat’s death in November and Abbas’ emergence as the new leader, the sides have expressed a desire and a willingness to coordinate the pullout.

The cease-fire declared in Egypt was meant to pave the way for coordination, but both Israel and the Palestinians have dragged their feet and made little progress in resolving key issues, such as who will take over the areas of Gaza that Israel leaves and what to do with the homes.

The current violence comes ahead of a Palestinian parliamentary election scheduled for mid-July in which Hamas is expected to make a strong showing against Abbas’ Fatah movement.

In New Delhi, Abbas expressed hope the truce he and Sharon declared Feb. 8 would hold. Fighting has dropped off sharply since the sides declared their truce, designed to end more than four years of conflict.

“I hope that all the parties will stick to the truce and they will not escalate (violence),” Abbas said. “Some incidents are taking place here and there, but I hope that we can contain and control all these incidents because the truce is in our interest and in the Israeli interest. So we have to preserve it.”

After the attack, about 100 Kfar Darom settlers, some of them armed, marched toward the abandoned building where the militants launched the attack, intending to set up a defensive position there. Israeli soldiers ordered them to turn back, and a brief scuffle between troops and settlers broke out.

The army, meanwhile closed Gaza’s main cargo crossing, citing security concerns.