France will back Palestinian attempts to upgrade their status at the UN General Assembly to a non-member "observer state".
The vote is scheduled to take place on Thursday in the 193-seat body.
"When the question is asked, France will vote yes," foreign minister Laurent Fabius told the lower house of parliament.
France is the first major European country to come out in favour of the bid.
A report on the EU Observer website showed that the Palestinian Authority could count on nearly half of all European Union nations for its application.
The Netherlands, which voted against a bid in 2011 to admit Palestine as a member of Unesco, is expected to switch sides.
Dutch foreign minister Uri Rosenthal has been replaced by the centre-left Frans Timmermans, a harsh critic of the Dutch government's pro-Israeli line.
He presented a motion in September calling on The Hague to back a Palestinian bid to get observer status in the UN.
Fabius' announcement came despite US efforts to prevent the Palestinian Authority from bringing the resolution to a vote.
"Our message to the Palestinians has not changed," an official told the Wall Street Journal.
"We believe that bringing forward a resolution on statehood is unwise, does not help bring them closer to their legitimate aspirations, and will create an environment less positive for negotiations. We are trying to prevent this from happening, don't want it to happen, and it has not happened yet."
The Financial Times reported that Britain was poised to back the Palestinian bid at the UN, if it received some assurances.
"The first is that the Palestinian Authority will not use the resolution to join the International Criminal Court or UN agencies," said the FT. "The second is that the Palestinians will not apply at the UN Security Council for full membership.
"Britain also wants reassurances that peace talks with Israel will carry on without preconditions."
The UK is trying to bolster the role of PA president Mahmoud Abbas, seen as a moderate alternative to Hamas.