Israel came away from talks with a U.S. mediator Sunday saying no new troop pullbacks from the West Bank can proceed without security pledges from the Palestinians.

Graphically underscoring Israel's security fears, a powerful car explosion killed at least one person Sunday night in the West Bank town of Ramallah. Israeli reports said authorities were investigating whether the explosives were meant to be used in a terrorist attack.Israeli Prime Minister Benjamin Netanyahu met Sunday night with U.S. envoy Dennis Ross for two hours.

Netanyahu's top aide, David Bar-Illan, said afterward that Palestinian leader Yasser Arafat had so far not backed the idea of reciprocal security steps in exchange for Israeli troop pullbacks.

"The main problem today was that Arafat has not yet replied to our questions and those of the Americans on how much he would be willing to do to comply with the security requirements set out by the United States," Bar-Illan told the Associated Press.

"There will be no redeployment unless we see some action on compliance," he said.

Ross and Netanyahu, whose meeting Sunday night was to have been their last, agreed to meet again Monday, Bar-Illan said.

After talking with Netanyahu, Ross went straight to Gaza for late-night talks with Arafat. Ross emerged from that nearly three-hour session saying he would report back to Washington about "refinements" to U.S. ideas that had emerged from several days of talks, but did not report any progress.

Arafat, who was to leave early today for the Netherlands, looked angry as he left the session.

Ross, who arrived in the region Thursday, has been shuttling between the two sides in an effort to break the yearlong impasse in the peace talks.

Earlier Sunday, Arafat welcomed what he said was an American proposal for an international summit in Washington, a meeting that could give him the political justification to continue the peace process even if Ross fails to win concessions from Israel.

Ross has been trying to win acceptance of a U.S. proposal for an Israeli troop pullback from about 13 percent more of the West Bank over 12 weeks. The withdrawal would be carried out in tandem with Palestinian moves to do more to fight terrorism.

Israel has said it cannot withdraw from more than 9 percent of the West Bank, and the Palestinians have demanded far more, but reports have circulated that a 10 percent to 12 percent pullback was being discussed.

Asked about reports that he would accept a 10 percent withdrawal, Arafat said, "This is still under discussion."

A senior Israeli official said Netanyahu and Ross did not discuss specific percentages Sunday night but would do so on Monday, Israel radio said.

Arafat's comment that he would welcome a Washington summit came after he was asked if he was ready to meet with Netanyahu. The two have met only once in the past year, in a meeting arranged by Ross in October.

"I am ready to have any meeting which will lead to results, and I welcome the idea suggested by the American initiative to hold a summit meeting in Washington, attended by a number of world leaders," Arafat said.

Bar-Illan said he did not know of such a proposal but noted that Netanyahu previously suggested a Camp David-style meeting with Arafat.

Meanwhile, Secretary of State Madeleine Albright told a coalition of American Jewish leaders that Israel must realize the United States is frustrated with the stalled peace process but reaffirmed the Clinton administration is "very determined" to break the stalemate.