Australian Prime Minister Tony Abbott has conceded he could lose his leadership at a Liberal caucus meeting where a leadership spill motion will be put.
A spill means the leadership is declared vacant, and open for re-election.
The motion - which is being put by two Western Australian MPs was due to take place on Tuesday.
But Mr Abbott has brought it forward a day, saying it was important to end the uncertainty.
The motion will be decided by secret ballot and at this stage there is no clear challenger.
Mr Abbott on Sunday said he wanted all MPs, including cabinet ministers, to vote freely.
"It's a pretty chastening experience to have a spill motion moved on you after just 16 months in government, a very chastening experience and I am determined that my government if it continues after tomorrow, will learn from this experience."
Mr Abbott is likely to face a challenge from his Communications Minister, Malcolm Turnbull, if the motion is carried.
So far neither Mr Turnbull or Foreign Affairs Minister Julie Bishop - the two MPs seen as the ministers most likely to replace Abbott - have said they would contest a leadership ballot.
However, one of Mr Turnbull's supporters expects the former Liberal leader will put himself forward, if the spill motion succeeds.
Another MP, who is on Mr Abbott's frontbench, said the statement was accurate.
The frontbencher added that while he had not decided how he would vote in the spill motion, he would most likely back Mr Turnbull if there was a vote for the leadership.
He also said if Mr Turnbull became Prime Minister, then Social Services Minister Scott Morrison was likely to become Treasurer.
There are 102 members of the Liberal party room, so the spill motion needs more than 51 votes to succeed.
The backbencher said he believed the number of MPs supporting the spill motion, so far, was more than 40.
The frontbencher also said he expected the vote on the spill motion would be "close" and that there was "a decent chance of it getting up" but, even in a secret ballot, he did not think many frontbenchers would back it.
The ABC understands supporters of both Ms Bishop and Mr Turnbull are continuing to make phone calls, urging them to run for the leadership.
The frontbencher said despite Ms Bishop saying she was against the spill motion, "there remains a real possibility she would run".
Another frontbencher said he spoke on the phone to both Mr Turnbull and the Prime Minister yesterday.
The Minister said he did not speak directly about the leadership with Mr Turnbull, describing the call as "friendly" and touching on "the state of play".
He said Mr Turnbull was "watching developments" but had not made a decision to run for leader.
The Minister said he did not believe the spill motion would succeed but it would have a better chance of getting up if Mr Turnbull declared his candidacy before the party room meeting.
South Australian senator Sean Edwards is willing to support Mr Abbott on the condition that the Prime Minister guarantees Australian shipbuilders will be allowed to bid to build the country's next fleet of submarines.
- ABC -