The US is not an honest broker and the peace talks with Israel have reached a deadlock, jailed Fatah leader Marwan Barghouti was quoted Sunday as saying.
Barghouti made his comments in a letter relayed by his lawyer to the Chinese news agency Xinhua.
Barghouti's comments seemed timed to come on the eve of US Secretary of State John Kerry's visit to the region - the fifth since he entered office - in a bid to revive stalled talks between the Palestinian Authority and Israel.
However Kerry, who was expected to arrive on Tuesday, has postponed his trip.
The State Department never formally announced when he would be coming back to the region, nor did the Prime Minister's Office officially announce that a meeting had been scheduled with Prime Minister Binyamin Netanyahu.
Both Israeli and US officials indicated the delay was due to scheduling problems stemming from Netanyahu's two-day trip to Poland on Wednesday. No new date for a visit has been announced.
Last week, at an address to the American Jewish Committee in Washington, Kerry said that he has visited Israel "in March, April, and May, and I will be back soon."
One Israel official dismissed some speculation that the postponement had to do with any problems in Kerry's efforts to re-launch Israeli-Palestinian talks, saying that if there was a crisis, Kerry would be definitely be coming to try and solve it.
Barghouti's statements are likely to embarrass Abbas and other PA leaders who have publicly supported Kerry's efforts to resume the peace negotiations.
"President Barack Obama has disappointed many in the world," Barghouti, member of the Fatah Central Committee who is serving five life terms in prison for his role in terror attacks on Israelis, said.
"Obama has failed in forcing Israel to abide by the requirements of the peace process. He has not shown a real desire until now in implementing resolutions of international legitimacy."
Barghouti claimed that Obama was responsible for blocking Palestinian attempts to gain full membership in the UN and its agencies and conventions.
Barghouti said that Obama and his administration have increased all forms of political and military aid to Israel.
He said that Kerry should ask Israel to "end occupation and establish a sovereign Palestinian state."
Barghouti said that Kerry must understand that Palestinians are not waiting for gestures from Israel, but are demanding their "scared national rights."
Referring to Kerry's plan to boost the Palestinian economy, Barghouti said that the Palestinians are opposed to "economic peace at the expense of their freedom, independence and the right of return" for Palestinian refugees to their former homes inside Israel.
Barghouti warned the PA leadership against returning to the negotiating table with Israel unconditionally, saying such a move would cause grave damage to the Palestinian national interests.
He said that the PA leadership should return to the negotiations only if Israel committed to "ending occupation and withdrawing to the 1967 borders, establishing an independent and sovereign Palestinian state with east Jerusalem as its capital, releasing all Palestinian prisoners and ensuring the right of return of all refugees."
Barghouti also rejected a proposal by the Arab League for land swaps between the Palestinians and Israel. The proposal was made last month during a visit by Arab League foreign ministers to Washington.
The Arab League is not authorized to make any concessions, Barghouti stressed.
He also voiced support for "popular resistance" against Israel, arguing that the right-wing government in Israel was not interested in peace with the Palestinians.
"Negotiations with Israel would not bear any fruits in the absence of resistance on the ground," Barghouti, who has been in prison since 2002, said. "The negotiations have reached a deadlock due to the extremist Israeli position and the absence of an Israeli partner."
In a related development, PA Foreign Minister Riad Malki warned that Israeli "intransigence" and refusal to halt settlement construction would sabotage Kerry's efforts to revive the peace process.
PLO Secretary-General Yasser Abed Rabbo said that the Israeli government was not interested in reaching a peace agreement on the basis of a two-state solution.
He said that the Israeli government was seeking to prevent the establishment of a Palestinian state by creating new facts on the ground.