The Palestinian leader has warned President Barack Obama that he will pull out of upcoming peace talks if Israel ends a slowdown on West Bank settlement construction, a Palestinian negotiator said on Monday.

President Mahmoud Abbas sent a letter to Obama stressing that any renewed Israeli settlement construction would end the talks, said Palestinian negotiator Saeb Erekat.

The direct negotiations are to begin in Washington next week, after months of US diplomatic efforts. Both sides seem pessimistic about the chances of success.

Israel's 10-month slowdown, which bars construction of most new homes in the West Bank, is supposed to end in late September, and Israel's government is split over whether to extend it.

Erekat said that Abbas also sent the letter to the European Union, the UN and Russia — all members of the Mideast Quartet of mediators, along with the US. "If the Israeli government continues settlement activities, then by this it would have decided to stop negotiations, because we can't continue with it if settlements continue," he said.

While Israeli Prime Minister Benjamin Netanyahu and other Israeli officials have said in the past that the slowdown would not be extended, the Israeli government is now signaling that it might be flexible.

"The government has yet to announce officially what will be done. For the moment, the most important thing is to get the talks going, and we're not going to do anything to give the Palestinians an excuse to derail the talks," said Yigal Palmor, a spokesman for Israel's Foreign Ministry.

Netanyahu has not commented on the issue of the freeze since the U.S. announced on Friday that talks would be resuming in Washington next week. It will be the first face-to-face peace talks between the sides since late 2008. Obama hopes to forge a deal within one year.

Extending the settlement slowdown would be deeply unpopular among the more hawkish members of Netanyahu's coalition government and among many members of his own Likud party.

Some analysts have suggested that in order to press ahead with the talks the Israeli leader might be forced to rearrange his coalition, excluding some of the more hard-line parties and bringing in his more moderate rivals from the opposition Kadima party.