The fate of the 17-month-old Abbott Coalition government will be the first order of business when Parliament resumes on Monday, with the 102-member Liberal party room considering a do-or-die spill of the prime ministership.

But as the meeting neared, Mr Abbott was leaving little to chance, throwing a last-minute bone to wavering South Australian Liberals by reversing an established policy and indicating he would allow Australian companies to bid for the multibillion-dollar future submarines project.

Late last year, Treasurer Joe Hockey had ruled out an open tender, arguing time had run out.

"We don't have time to go through a speculation process," he told ABC radio at the time. "We do not have time for people to suggest that they can build something that hasn't been built. We don't have time for that because Labor failed to make decisions."

One MP, who said he would still vote for a spill, questioned how Mr Abbott could have made the announcement, suggesting it had not been to cabinet or its national security committee.

The special party room meeting will take place in Parliament House at 9am, after being unilaterally brought forward by 24 hours by Mr Abbott.

That tactical decision, branded another "captain's call" by Malcolm Turnbull, who is considered the prospective challenger, came just hours after Mr Turnbull had praised Mr Abbott for sticking to the Tuesday timetable in the interests of allowing consultation between MPs.

"The Prime Minister's decision had been, as he said, to hold the meeting on Tuesday and I did praise him for that this morning," Mr Turnbull said.

"Look, he's the Prime Minister. He's made a captain's call. He's changed the date of the meeting," he said.

It came in a day of continued shadow-boxing and veiled threats, during which Mr Turnbull resisted pressure to launch a frontal challenge.

A plan to announce his candidacy late on Sunday was abandoned, with Mr Turnbull eager to allow the spill motion to be debated free of his involvement.

Mr Hockey told Sky News that any cabinet minister who wanted to support the spill or seek the leadership should resign immediately.

Mr Abbott's supporters acknowledged the rescheduling reflected his growing confidence that he could see off those agitating for a change with as much as 60 per cent of the votes, and wanted to "get it done" rather than allow the situation to fester.

The Turnbull camp was weighing its approach on Sunday, with backers eager to see the Communications Minister declare his intention to the seek the leadership.

They argued this could swing support away from Mr Abbott, because MPs would have an alternative candidate to focus on.

A Fairfax Ipsos poll taken at the weekend found support for the state Liberal government in NSW was suffering from the poor standing of its federal counterpart, with one in 10 Liberals supporters at the last state election saying the federal government's performance had changed the way they would vote.

On Sunday afternoon, however, just five MPs were prepared to say publicly they supported the spill motion in the absence of a candidate, while at least 20 MPs declared they would back the Prime Minister and oppose the motion.

Mr Turnbull, Foreign Minister Julie Bishop and Social Services Minister Scott Morrison spoke on Sunday afternoon to discuss the leadership.

Mr Morrison has been tipped to take on the Treasury portfolio if Mr Turnbull was to become prime minister, while Ms Bishop has been tipped to remain Foreign Minister. Liberal MPs Arthur Sinodinos, Sharman Stone and Dennis Jensen joined Luke Simpkins and Don Randall in publicly backing a spill.

In a stinging rebuke to Mr Abbott, Senator Sinodinos, who served as chief of staff to former prime minister John Howard for a decade, also suggested Ms Bishop had not been consulted.

"I will vote for a spill, as that will help precipitate a discussion," he said.

Senator Sinodinos is well respected in the Coalition and his criticism will carry significant weight in the Liberal party room.

"I am disappointed the party room meeting has been brought forward. MPs should be given adequate time to discuss the matter at hand," he said

"If for whatever reason the leadership of a political party is vacant then any member of the party can stand, whether they be a minister or a backbencher, without any disloyalty to the person whose leadership has been declared vacant."

But other Liberal MPs, including Finance Minister Mathias Cormann and Queensland Senator Ian Macdonald, backed the Prime Minister's decision to bring forward the spill motion to Monday.

Senator Cormann told the ABC's Insiders program the move "provides a certainty for the party and for the country. My colleagues are all professionals. This issue has been discussed among colleagues for some time now.

"It's inconceivable that it would be in the best interests of either the Liberal Party or the country for the Prime Minister to go into the Parliament tomorrow with this issue unresolved."

Other Liberal MPs to support Mr Abbott and opposition to the spill motion were Immigration Minister Peter Dutton, Speaker Bronwyn Bishop, Karen Andrews, Russell Broadbent and Ian Goodenough.