Hamas on Sunday said it would not back a UN membership bid, and warned that no Palestinian leader had a mandate to sacrifice fundamental Palestinian rights.
Hamas prime minister Ismail Haniya, speaking in Gaza, said the group also continued to support the establishment of a Palestinian state on any part of "historical Palestine" but would not seek to disrupt the UN bid.
His comments came as Palestinian president Mahmud Abbas heads to New York to submit a formal bid for UN membership for a Palestinian state on the lines that existed before the 1967 Six Day War.
Speaking to a meeting of the Palestinian legislative council, Haniya warned that Palestinian rights must be protected.
"There is no mandate for any Palestinian leadership to infringe on Palestinian national rights, nor is there a mandate for any Palestinian actor to make historic concessions on Palestinian land or the right of the Palestinians, foremost among them the right of return," he warned.
"Given this position, we reiterate our rejection of this bid," he added.
But the leader of the Islamist group that rules the Gaza Strip stressed that Hamas would "not place obstacles in the way of the establishment of a Palestinian state with full sovereignty."
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"We repeat today that we are with the establishment of a Palestinian state on any liberated part of Palestinian land that is agreed upon by the Palestinian people, without recognising Israel or conceding any inch of historical Palestine."
Hamas has made clear it will not throw its support behind Abbas's move, but has toed a cautious line, choosing not to condemn the plan directly.
Speaking during the meeting, senior Hamas official Khalil al-Hayya said the legislative council should approach the UN for recognition of a Palestinian state on all of "historical Palestine," including areas now in Israel.
He called on the council to "apply for recognition of a Palestinian state on all the Palestinian territory and confirmation of the right of Palestinians to live within the borders of this state."
"We appeal to the UN to invalidate the entity that took the decision to establish itself on the land of another," Hayya said, in reference to Israel.
Hayya called on the international community to "apply pressure to ensure the implementation of international resolutions, particularly those that uphold the right of the Palestinian people to self-determination."
Abbas is expected to present later this week a formal request for UN membership of a Palestinian state on the pre-Six Day War lines, encompassing both Gaza and the West Bank, including annexed Arab east Jerusalem.
The bid is fiercely opposed by Israel and the United States and has divided much of the international community, with Europe and Washington organising last-minute diplomacy in an attempt to head off a Security Council vote on the measure.