Prime Minister Scott Morrison said no decision will be taken before the election on whether to choose a US or UK model for Australia's nuclear-propelled submarines.
The statement, made following a speech to the Lowy Institute forum on Monday, downplays a suggestion the decision on the submarines could be fast-tracked.
Defence Minister Peter Dutton had told the ABC's Insiders program on Sunday an announcement would be made "within the next couple of months about which boat we are going with [and] what we can do in the interim".
But Mr Morrison rejected this timeline when questioned about the possibility.
"We don't anticipate that should be before the election and no one should expect it to," he told reporters.
"It won't be done in that time frame."
The Australian government is currently working with partners in the AUKUS alliance through an 18-month process to determine how to deliver the submarine project, which was first announced last September.
This would move the time frame for a decision to within the first half of 2023.
Mr Morrison on Monday also announced a base for Australian and visiting nuclear-powered submarines would be set up on the east coast as part of the plan.
He told the Lowy Institute forum that defence officials have been tasked with talking to the NSW and Queensland governments on setting up the multibillion-dollar base at either Brisbane, Newcastle or Port Kembla.
Australian Prime Minister Scott Morrison gave a virtual address of the Lowy Institute. Credit: SUPPLIED/PR IMAGE
"(But) establishing a second submarine base on our east coast will enhance our strategic deterrent capability, with significant advantages in operational, training, personnel and industrial terms," Mr Morrison said.
"An optimal east coast base would provide home-ported submarines with specialised wharves, maintenance facilities, administrative and logistics support, personnel amenities, and suitable accommodation for submarine crews and support staff.
"It would also enable the regular visiting of US and UK nuclear-powered submarines."
With initial work to be completed by the end of 2023, the three potential sites have been chosen because of their proximity to industrial infrastructure, large population centres, deep water, maritime training and weapons storage and loading facilities.
Mr Morrison said more than $10 billion would be needed to meet the services and facilities needed for the shift from Collins to the nuclear-powered submarines.
Mr Dutton on Sunday also said he was confident the first of the submarines could be acquired "much sooner" than 2040.
Opposition Leader Anthony Albanese on Monday said the government needed to focus on delivering the project, rather than playing politics with announcements.
"How about we treat national security in the way it should be, which is a bipartisan way with considered sober analysis and with announcements that actually lead to outcomes," he told reporters.
Labor has given its in-principle support for the AUKUS alliance.
The massive project comes as Australia faces what Mr Morrison describes as its most "difficult and dangerous security environment in 80 years".
The government is lifting defence spending to almost 2.1 per cent of GDP this year, with $578 billion planned to be spent over the next decade.
The prime minister told the forum the "unprovoked, unjust and illegal war" launched by Russia in Ukraine was a sign of a "new arc of autocracy" seeking to challenge and reset the world order.
"We face the spectre of a transactional world, devoid of principle, accountability and transparency," he said.
The implications of the Ukraine crisis would not only be felt in Europe but inevitably stretch to the Indo-Pacific.
"Militarisation is expanding and evolving rapidly," Mr Morrison said.
"Australia seeks to work with all countries to ensure a peaceful, stable and prosperous region - however, we cannot be naïve.
"The challenges we face continue to mount. They require us to increase our resilience, expand our capabilities and harden our defences."
