The federal government will attempt to have the Senate sit beyond Thursday to try to force a vote on its carbon tax repeal legislation.
The move will fail if Labor and the Greens gang up on the coalition in the upper house.
Government senate leader Eric Abetz wants senators to remain in Canberra for as long as it takes - up to Christmas if necessary.
The Senate so far has voted on only one of the 11 bills in the government's repeal package.
Nor has it voted on a bill to repeal Labor's minerals resource rent tax.
Senator Abetz says the government has a "thumping mandate" to get rid of the carbon tax.
"The Labor and Green alliance in the Senate is seeking to deny that legislation getting through before Christmas," he told reporters in Canberra on Wednesday.
Greens senator Richard Di Natale said his colleagues would consider extending sitting hours at a party meeting on Wednesday morning.
But party leader Christine Milne already has said she won't be in Canberra past Thursday, when parliament is due to rise for the long summer break.
It doesn't return until mid-February.
Independent senator Nick Xenophon flagged his support for the government move.
"We have got a job to do to deal with legislation one way or the other and we should just get on with it," he said.
A spokesman for Senator Di Natale later said the Greens would oppose any government move to extend Senate sitting hours.
