Scott Morrison has Liberals' support for a 2050 net zero emissions reduction target but Nationals MPs still aren't convinced.
The junior coalition partner still hasn't backed a proposal which would allow the prime minister to take the goal to a major climate conference in Glasgow next month.
Nationals leader Barnaby Joyce admits he remains cynical and cautious about approving the target, but insists he will fight for his party's consensus position.
Mr Joyce said Mr Morrison had received a mandate from the majority of Liberal MPs for his climate policy.
"It's his right as the prime minister to determine a whole raft of things," he told Sky News.
But he said the Nationals were a separate party with its deliberations focused on what long-term climate change action would mean for regional jobs.
"I have no mandate from the Nationals party room at this stage so I can't offer to the coalition a coalition mandate."
Mr Joyce indicated the government had commodity price modelling pointing to an negative impact on demand for Australia's coal.
He said Mr Morrison would know the Nationals demands by the end of the week.
"This is not grandstanding, this is not ransom," he told parliament.
"This is making sure that we do our job and we will continue to do our job."
Mr Morrison has four Nationals in his 23-member cabinet which will meet on Wednesday.
The prime minister has been adamant cabinet will make the final decision.
Cabinet ministers who oppose government policy would be forced to quit.
Mr Joyce, Agriculture Minister David Littleproud, Emergency Management Minister Bridget McKenzie and Veterans' Affairs Minister Andrew Gee make up the Nationals' cabinet contingent.
The contentious issue was not mentioned when Mr Morrison and Mr Joyce addressed a meeting of coalition MPs in Canberra on Tuesday.
Some Nationals remain staunchly opposed to the 2050 target, while senior Liberal cabinet ministers are making the case to sign up.
Labor leader Anthony Albanese described the situation as a Nationals pantomime which would end with Mr Morrison taking the commitment to Glasgow.
"But he'll pretend that that's sort of a big victory without a real path to get there," he said.
"You have the absurdity of people who are National Party ministers and frontbenchers, including cabinet ministers, no less than the deputy prime minister, not supporting the government's policy."
The government has ruled out raising its 2030 emissions reductions targets from 26 to 28 per cent, while the opposition will release medium-term goals before the election.
