Top Palestinian officials have questioned the veracity of leaked documents purporting to show offers of major concessions to Israel.
The documents, obtained by al-Jazeera, suggest the Palestinians agreed to Israel keeping large parts of illegally occupied East Jerusalem - an offer Israel apparently rejected.
But chief negotiator Saeb Erekat said the leaks were "a pack of lies".
The BBC has been unable to verify the documents independently.
Al-Jazeera says it has 16,076 confidential records of meetings, emails, communications between Palestinian, Israeli and US leaders, covering the years 2000-2010.
The Palestinians are reported to have proposed an international committee to take over Islamic holy sites in Jerusalem, and limiting the number of returning refugees to 100,000 over 10 years.
The papers are believed to have leaked from the Palestinian side.
But Mr Erekat appeared to challenge their authenticity, saying the Palestinian leadership had nothing to hide.
"We have not gone back on our position," he told al-Jazeera.
"If we had given ground on the refugees and made such concessions, why hasn't Israel agreed to sign a peace accord?"
Palestinian Authority President Mahmoud Abbas, who is due to hold talks on the Middle East peace protest on Monday with Egyptian President Hosni Mubarak, also raised doubts about the leaks.
"I don't know from where al-Jazeera came with secret things," he was reported to have told Egyptian newspaper editors in Cairo.
Current peace talks between Israel and the Palestinians have been suspended for months, ostensibly over Israel's refusal to stop building Jewish settlements on occupied Palestinian land.
The BBC's Wyre Davies, in Jerusalem, says there has been increasing frustration and protest among many Palestinians over what they see as Israeli expansion and the weakness of their own leaders - a view that will be reinforced by the leak of these documents.
'Biggest Yerushalayim'
Among the leaked papers, the alleged offers relating to East Jerusalem are the most controversial, as the issue has been a huge stumbling block in Mid-East talks and both Israelis and Palestinians claim Jerusalem as their capital.
Israel has occupied the West Bank, including East Jerusalem, since 1967, establishing close to 500,000 Jews in more than 100 settlements.
According to al-Jazeera, in May 2008, Ahmed Qurei, the lead Palestinian negotiator at the time, proposed that Israel annex all Jewish settlements in East Jerusalem except Har Homa (Jabal Abu Ghneim), in a bid to reach a final deal.
"This is the first time in history that we make such a proposition," he reportedly said, pointing out that this was a bigger concession than that made at Camp David talks in 2000.
"We are offering you the biggest Yerushalayim in Jewish history," Mr Erekat was quoted as saying, using the Hebrew word for Jerusalem.
Palestinian Liberation Organisation (PLO) leaders also privately suggested swapping part of the flashpoint East Jerusalem Arab neighbourhood of Sheikh Jarrah for land elsewhere, according to the leaks.
In addition, Palestinian negotiators are said to have proposed an international committee to take over Jerusalem's Temple Mount, which houses the Dome of the Rock and Al-Aqsa Mosque - Islam's third holiest site.
And they were reported to be willing to discuss limiting the number of Palestinian refugees returning to 100,000 over 10 years.
The leaks also purport to show that Palestinian leaders had been "privately tipped off" about Israel's 2008-2009 war in Gaza, a claim Mr Abbas has denied in the past.
US 'bias?'
These highly sensitive issues have previously been non-negotiable.
The Israelis apparently rejected the concessions and made no offer in return.
Also the reportedly curt dismissals by some US politicians of Palestinian pleas do not fit with the message of even-handedness that President Obama tried to put across in his 2009 Cairo speech, says the BBC's Jonny Dymond in Washington.
The Palestinian ambassador to the UK, Manuel Hassassian, said that if confirmed, the documents would show that "major concessions" had been offered.
"But I think we need to see this in context," he told the BBC World Service's World Today programme.
"What was Israel willing to give in return to these concessions? Nobody talks about the other side."
