EHUD Olmert, the Israeli prime minister, last night agreed to meet Palestinian leaders to try to resume negotiations on an internationally backed peace plan.
Following talks with Hosni Mubarak, the Egyptian president, Mr Olmert said he would insist that the Palestinians carry out their commitments under the plan, known as the "road map". Those include dismantling violent groups.
Mr Olmert did not give a date for his meeting with Mahmoud Abbas, the moderate Palestinian president.
It will be the first summit meeting between Israeli and Palestinian leaders since February 2005.
Mr Abbas has tried to control militants through negotiations, but the Hamas victory in elections and formation of a government have undermined his efforts.
Mr Olmert said his first priority now is to resume peace talks with the Palestinians, leaving his plan to unilaterally draw Israel's border with the West Bank as a second option.
Mr Olmert said: "I really hope that our Palestinian partners will take advantage of this opportunity and will implement all their commitments so that it will be possible to proceed according to the road map."
Mr Mubarak refused to give his opinion over a dispute between the Hamas-led Palestinian government and Mr Abbas over a document implicitly recognising Israel.
The militant Hamas government yesterday defied an ultimatum issued by Mr Abbas over the issue.
Expiry of the deadline - at midnight tonight - without agreement, would set the stage for renewed, heightened violence between Hamas and Mr Abbas's Fatah movement, amid fears of an all-out civil war.
According to the ultimatum, issued on 25 May with a ten-day deadline, Hamas would have to agree to the principles of the peace plan, or the matter would be put to a vote in a national referendum.
Mr Abbas's spokesman, Walid Awad, said the president would issue an order tomorrow on the holding of a referendum, unless Hamas changed its stance at the last minute and agreed to the document's provisions. They include the formation of a national unity government and the establishment of a Palestinian state next to Israel.
Mr Abbas believes gaining wide Palestinian support for the document would enable him to thwart Israel's bid unilaterally to annex parts of the West Bank by refuting its claims that there is no Palestinian partner for negotiations.
But in his strongest statement yet on the matter, Ismail Haniya, the Hamas prime minister, yesterday said the referendum idea was illegal.
"The local basic law and the advice we got from experts in international law say that referendums are not permitted on the Palestinian land," he said.
But Mr Haniya added that "from a political point of view, the holding of a referendum necessitates serious studies".
Mr Abbas was sending personal emissaries to Mr Haniya to get a final response from him, aides said.
Hamas, whose charter calls for Israel's destruction on the grounds that all of historic Palestine is sacred Islamic territory, has refused to give in to international demands that it recognises Israel, renounces violence and upholds existing Palestinian Authority agreements with the Jewish state.
As a result, international assistance has been withheld and the Palestinian territories have been plunged into a severe economic crisis, endangering the existence of the government because it is unable to pay its 165,000 workers.
Yesterday saw signs of relief when a Palestinian bank began paying some government workers a month's salary, despite threats of sanctions against institutions dealing with the Hamas government.
Hani Masri, a Palestinian analyst, said it was likely Mr Abbas would call the referendum, but might wait a few more days. He predicted this would lead to intensified clashes between Fatah and Hamas, which resulted in 11 deaths last month.
"Hamas has an interest in escalation, in creating an atmosphere where the referendum cannot be held. It would like to run away from the referendum," he said.
The weekend saw the first appearance of a new Fatah militia. More than 2,000 men in black T-shirts and white headbands marched through the West Bank town of Jenin on Saturday - a rival force to a 3,000-strong Hamas militia the government mobilised last month.