Speaking in New York, Palestinian president Mahmud Abbas said Washington had done "everything in its power" to stop him from delivering the request to UN chief Ban Ki-moon later on Friday, but insisted he would not be deterred from seeking what was a basic Palestinian right.
"We are going tomorrow," he told a group of hundreds of Palestinian-Americans who came to his hotel late on Thursday, on the eve of the key meeting with Ban.
"The American administration did everything in its power to disrupt our project but we are going through with it despite the obstacles and the pressure because we are asking for our rights," he said.
"There are small countries in the world that have gained their freedom and independence but we still haven't got ours."
"So we are going to demand this right and give the application to Secretary General Ban Ki-moon so he can give it to the Security Council."
Abbas is scheduled to hand over the membership request when he meets Ban at 11:35 am (1535 GMT), shortly before making a speech to the UN General Assembly in a move which is adamantly opposed by both Israel and Washington.
"We have been under occupation for 63 years waiting for our freedom. No-one could put up with what we have been through," he said.
His allusion to "63 years" of occupation was likely to spark controversy over its clear reference to 1948, the year in which Israel was established, rather than 1967 when the Jewish state occupied the West Bank, Gaza Strip and east Jerusalem -- areas which the Palestinians say they want for their future state.
The Palestinians say the move to seek UN membership emerged out of frustration with the complete lack of progress in peace talks with Israel, which ground to a halt last autumn in a dispute over Jewish settlement building.
Both Israel and the US say a Palestinian state can only emerge out of bilateral negotiations, and argue that the appeal to the UN will damage any attempt to broker a negotiated peace deal.
"We tried to make some progress through negotiations but no progress has been made with this current Israeli government," Abbas said.
"We told the Israeli government and the mediators and the Quartet: if you want to go back to negotiations, we want two things only -- stop the settlements and accept a Palestinian state on the 1967 lines with minor adjustments.
"In this case, we can go back to negotiations, but without it, we can never go back."
Israel has been calling for an immediate return to the negotiating table "without preconditions."
But the Palestinians say they will not talk while Israel builds on land they want for a future state, nor will they enter negotiations which do not accept the pre-1967 lines as the basis for starting talks.
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