Hamas, which seized control of Gaza from Abbas in 2007, argues that negotiations with Israel are a waste of time, but Hamas leaders have come out in support of the U.N. bid in recent days.
During Israel's Gaza offensive, Abbas was largely sidelined at his compound in the West Bank, underscoring international concerns that the deadlock in peace efforts is increasingly weakening him and other Palestinian pragmatists.
Abbas aides have said they expect key European countries to support the U.N. bid at the last minute in an attempt to strengthen Abbas.
On Tuesday, France announced its support, followed on Wednesday by similar pledges from Spain, Norway, Denmark and Switzerland. Germany said it would not support the initiative.
Israel appeared to be backing away from plans to immediately punish the Palestinians for going to the U.N. Instead, an Israeli government official said Israel would wait to see whether the Palestinians would use the world body's expected approval to hurt Israel.
The Palestinians plan to seek membership or access to a number of international and U.N. agencies, including the International Criminal Court, once their statehood bid is approved.
Israel would respond "forcefully" if the Palestinians try to pursue war crimes charges against Israel at the ICC, said the official, who spoke on condition of anonymity to discuss policy considerations. If the Palestinians use their upgraded international status "as a tool to confront Israel in the international arena, there will be a response."
Until then, he said, Israel will be bound by its obligations to the Palestinians under existing peace agreements, but won't necessarily go beyond them. Earlier there was talk of Israel's retaliating by canceling the partial peace accords.
Associated Press writer Amy Teibel in Jerusalem contributed reporting.
Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.