Australia is confident the U.S. will follow through with the sale of nuclear-powered submarines as part of the AUKUS deal, a minister said on Wednesday, after mooted cuts to the U.S. program sparked concerns the deliveries could be delayed or scrapped.

Under the AUKUS partnership signed in 2021, the United States will sell Australia between three and five Virginia-class attack submarines from the early 2030s as a stopgap while Australia and Britain build a new SSN-AUKUS class due roughly a decade later.

Fears that long-standing backlogs at U.S. shipyards and a shrinking submarine fleet could undercut willingness for the sales boiled over this week when the Biden administration cut its funding request for the Virginia class.

Defence Industry Minister Pat Conroy said Australia had total confidence in the AUKUS deal and that the U.S. was making good progress upgrading its shipyards so they could produce the Virginia class for both navies.

"I see a lot of hyperbolic headlines about the death of AUKUS, I think it's the fourth time AUKUS has died in the last year," he told Reuters by phone.

"We remain very confident that we'll be in a position for the Virginia class to be sold to Australia on the timeframes articulated."

The U.S. navy is building an average of slightly more than one Virginia-class submarine a year, well short of the estimated 2.33 needed to grow its fleet and sell Australia boats.

At a budget briefing on Monday, U.S. Under Secretary of the Navy Erik Raven said the submarine industrial base was stressed, but an $11.1 billion, five-year investment in the budget request plus a promised $3 billion from Australia as part of AUKUS would lift production to target.

But by the time the sales near in 2030, the number of attack submarines in the U.S. navy is set to fall to a historic low of 46 versus a target of 66, according to Michael Shoebridge, founder of Strategic Analysis Australia and a former defence official.

"It's going to get harder for a commander of the U.S. submarine force to say, no, I can get by with less submarines, I'm happy to sell three to my Australian friends," he said.

"A U.S. president will come under more pressure to say, I need to look after my own security first."

Former Prime Minister Malcolm Turnbull, whose plan to buy French submarines was scrapped by his successor in favour of AUKUS, said on Wednesday the U.S. was unlikely to make its own deficit worse by sending submarines to Australia.

"This is really a case of us being mugged by reality," he told the Australian Broadcasting Corp. (Reporting by Lewis Jackson; Editing by Jamie Freed)