Palestinian President Mahmoud Abbas arrived in New York poised to demand full membership for a Palestinian state at the UN General Assembly.
The Palestinians see it as the only way for short term progress to statehood after nearly 20 years of on-off talks now at a standstill.
Washington and Israel say a UN vote on Palestinian statehood would damage any chance for peace talks.
They argue that a state can only be created through a settlement between the two sides.
Senior diplomats from the U.S., Russia, the European Union and the UN are scurrying to avert what could be an embarrassing row.
Israel's deputy foreign minister says a Palestinian request for full UN membership would do more harm than good.
SOUNDBITE: Danny Ayalon, Israeli deputy foreign minister, saying (English):
"We have enough tumult in the region that we do not need another element of instability which may occur in the wake of a Palestinian unilateral action here in the United Nations.
Former UK Prime Minister Tony Blair, now an envoy for the Mideast international mediators, says a crisis can still be averted.
SOUNDBITE: Tony Blair, envoy for Mideast Quartet of Middle East negotiators, saying (English):
"What we should aim for this week is to have a significant advancement of Palestinian statehood and the negotiation restarted because that then allows us to combine strong support from the international community for Palestinian statehood with a relaunched and revitalised new negotiation."
Western officials are hoping to head off a full-scale UN confrontation with an offer of timeframes, however vague, to address Palestinian calls for quick action.
Any offer would come with an unchanged message from the U.S. that it would veto a Palestinian bid for UN recognition and membership.
Paul Chapman, Reuters