The Palestinian leadership -- despite firm US and Israeli opposition -- will give the UN Security Council "some time" to study their application for full membership in the United Nations, a senior Palestinian official said on Wednesday.

He also said the Palestinian delegation would politely reject US President Barack Obama's demand in his UN General Assembly speech on Wednesday that the Palestinians drop their bid for membership in the United Nations, a plan that is doomed to failure if Washington keeps its promise to veto it.

"We will give some time to the Security Council to consider first our full membership request before heading to the General Assembly," Nabil Shaath, a senior official in President Mahmoud Abbas' Fatah party, told reporters on the sidelines of the UN General Assembly.

Some UN diplomats and officials have said that the 15-nation Security Council might buy time by dragging out its review of the Palestinian UN membership application, which Abbas has vowed to submit on Friday to the UN chief Ban Ki-moon.

That review, they say, could theoretically take months, or even years.

"Any delay will be part of the procedure," Shaath said, adding that if there was an "undue delay," the Palestinians would turn to the General Assembly.

By turning to the General Assembly, Shaath was referring to a second UN option the Palestinians have been considering alongside full UN membership.

The second possibility is the so-called "Vatican option," under which the Palestinians would seek status as a non-member observer state in the United Nations, which would enable them to join the International Criminal Court and sign other international treaties and covenants.

The Palestinians are currently an observer "entity" at the United Nations.

It would not be difficult for the Palestinians to gain non-member state status, like the Vatican, as it would not need Security Council approval and would require only a simple majority approval in the 193-nation General Assembly. It would also be an indirect recognition of Palestinian statehood.

Full membership requires Security Council approval and a two-thirds majority in the General Assembly.

Shaath said Abbas would make all of this clear to Obama at their meeting on Wednesday night.

"When we meet President Obama we will re-explain our issue, why we have to have United Nations membership," Shaath said.

"We will really cordially and respectfully tell him 'No'. We are insistent," he said. "This is morally, politically, and legally correct what we are trying to: joining the United Nations."

At the sidelines of the global meeting, Obama told Abbas on Wednesday that UN action would not achieve a Palestinian state and the United States would veto any Security Council move to recognize Palestinian statehood, the White House said.

"We would have to oppose any action at the UN Security Council including, if necessary, vetoing," Ben Rhodes, the White House national security council spokesman, told reporters after Obama met Abbas in New York.

Earlier, an official, who spoke on condition of anonymity, said US Secretary of State Hillary Clinton would also hold separate meetings with Mahmoud Abbas and Israeli Prime Minister Benjamin Netanyahu on Wednesday evening,

But President Abbas seemed determined to press ahead, even after face-to-face talks with Obama, underscoring the stark new limits of US influence -- and of Obama's own personal clout -- in the restive region.