The Abbott government appears to be backtracking on Labor's controversial and expensive promise to build 12 advanced new submarines.
Defence Minister David Johnston will tell a conference in Canberra on Wednesday the commitment to acquire the 12 subs should not be taken as a given.
It comes with some good news: a report to be released at the conference says the Navy's six troubled Collins submarines are now performing better than ever.
It follows a scathing 2012 report by UK submarine expert John Coles, who found their availability fell short of comparable international submarine services.
As well, time in maintenance was about a third greater and percentage of days lost due to defects was double the international standards.
In his latest review, Mr Coles found a concerted effort by Defence and shipbuilder ASC has paid off with an encouraging turnaround.
The Collins boats will start retiring in the 2030s.
Labor's 2009 defence white paper outlined an ambitious program for 12 new submarines, with greater range and endurance and superior capabilities to their predecessors, to be built in Australia.
The commitment was repeated in the 2013 white paper in a program of unprecedented scale and complexity, which would span decades.
No price tag has been cited, although analysts from the Australian Strategic Policy Institute, which is hosting Wednesday's conference, suggest a maximum around $40 billion for the most expensive option of a brand new design.
Senator Johnston will also tell the conference Defence is not a job creation agency and contracts for new navy vessels will have to be based on performance.
The Australian Manufacturing Workers' Union says it's vital the navy's ships and submarines be designed and built in Australia.
Having an industry that employed people in the defence of Australia was about protecting the national interest, assistant national secretary Glenn Thompson said.