GAZA CITY, Gaza Strip ? Hamas quit talks Friday on halting anti-Israeli attacks, a decision that jeopardizes the U.S.-backed peace plan. But Palestinian officials insisted a truce was still possible and pushed ahead with plans to get illegal guns off the streets, including a weapons buyback.

As part of the U.S.-backed “road map” to Palestinian statehood, the Palestinians have to disarm and dismantle militant groups that have killed hundreds of Israelis in shootings and bombings in 32 months of fighting.

Palestinian Prime Minister Mahmoud Abbas has been trying to negotiate with the militias rather than use force, and said earlier this week he was optimistic he could broker a truce within a week.

A Hamas refusal to negotiate could force Abbas to make a difficult choice: either crack down on the group and risk civil war, or allow it to continue bombings and shootings that would derail Washington’s peace efforts.

The White House underlined that Palestinian leaders must still ensure a stop to attacks on Israel.

“There is now a real prospect for peace,” said Michael Anton, a spokesman for the White House’s National Security Council. “All parties agreed … that terrorism has to stop and that all parties have an obligation to fight terror. Those who pursue terror have made it clear they want to prevent peace.”

Palestinian officials say the Hamas walkout may not be final. Hamas, known for its pragmatism, would not risk a confrontation with security forces and would quickly resume talks, they said.

Palestinian Cabinet Minister Ziad Abu Amr, Abbas’ liaison to Hamas, blamed Israel’s overnight killing of two Hamas militants near the West Bank city of Tulkarem for the breakdown in talks.

But Hamas officials said they were angry at Abbas’ concessions at a summit Wednesday in Jordan. At the meeting with President Bush and Israeli Prime Minister Ariel Sharon, Abbas, also known as Abu Mazen, called for an end to the “armed intefadeh.”

“We were shocked when we saw Abu Mazen and his new government giving up all the Palestinians’ rights,” said Abdel Aziz Rantisi, a Hamas official. “Abu Mazen committed himself in front of Bush and Sharon to very dangerous issues that closed the door of dialogue between us.”

Other efforts to clear the streets of gunmen continued, with Palestinian security chief Mohammed Dahlan offering to buy illegal weapons carried by members of the Al Aqsa Martyrs’ Brigades. The buyback was to start in the coming days, they said.