Palestinian leader Mahmoud Abbas has called for a session of the UN Human Rights Council to vote on a report accusing Israel of war crimes in Gaza.
Mr Abbas has faced a week of angry criticism after the Palestinian Authority backed deferring the vote until March.
On Sunday he said there had not been enough support for the vote.
Hamas's leader in Damascus called the issue a "scandal" that would harm Palestinian unity efforts.
Mr Abbas was speaking in a televised address, widely seen as an attempt to restore his standing in the wake of the withdrawal of Palestinian backing for the report by UN investigator Richard Goldstone.
The report accuses both Israel and Hamas of committing war crimes during Israel's 22-day operation in Gaza which began in December 2008.
"Since we felt that we would not be able to gather enough support, we asked for the postponement of the draft resolution until the upcoming session of the Human Rights Council," he said, by way of explanation.
Mr Abbas had already ordered an "investigation" into how his own government made the decision.
He said he had now instructed his officials to push for a special session of the UN Human Rights Council to bring forward the debate that the PA had earlier supported deferring until March.
'Mistakes'
The council could choose to refer the report to the UN Security Council, which has the power to ask the International Criminal Court to open a war crimes prosecution.
Khaled Meshaal, the Syria-based leader of Hamas, said the decision to back deferring the vote was "a scandal" and "the final straw", and Hamas could "not accept any more mistakes".
"This is not a leadership which deserves our trust," he said.
The group said it had delayed talks to end a bitter feud with Mr Abba's Fatah faction.
The rival movements had been due to sign a deal paving the way for fresh elections in the first half of 2010 in late October.
Egypt's foreign minister said on Sunday that the reconciliation might be postponed "for a few weeks".
No agreement on talks
Israel has dismissed the Goldstone report as flawed and intrinsically biased.
It reacted angrily on Sunday to comments by the UK's ambassador to the UN in support of elements of the report.
Israeli officials suggested that if the same legal arguments were applied to British conduct in Afghanistan and Iraq as in Gaza, the UK could find itself in the dock.
"London is waging its own war against terror, and they might find themselves with their hands tied if they back Goldstone's recommendations," the Israeli newspaper Haaretz quoted unnamed officials as saying.
Also on Sunday, US Middle East envoy George Mitchell ended a visit to the region without getting a commitment from Israeli and the Palestinian officials on the resumption of stalled peace negotiations.
Israel's right-wing government has refused to meet the Palestinian demand that it comply with previous pledges to freeze all settlement activity before talks can resume.
According to comments reported in the Palestinian press, Mr Meshaal apparently also reversed previous statements suggesting Hamas would accept a Palestinian state in the West Bank and Gaza.
"After the Arabs offered all the possible initiatives and after the Israelis and the Americans rejected their initiatives, the Arabs and the Palestinians must go back to their original demands," he said.
"We must say: Palestine from the sea to the river, from the west to the occupied east, and it must be liberated," he said, referring to the land between the Jordan River and the Mediterranean Sea and therefore the state of Israel.
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