Twenty-five US Republican lawmakers have urged President Joe Biden to increase funding for the country’s submarine fleet, citing the AUKUS project to supply Australia with nuclear-powered submarines and concern about China’s increasing military might.

“We support the vision of the Australia-United Kingdom-United States (AUKUS) partnership and its potential to change the strategic landscape in the Indo-Pacific,” the lawmakers said in a letter.

“The AUKUS agreement is vitally important but we must simultaneously protect US national security.”

They said the plan to sell three attack submarines to Australia would “unacceptably weaken” the US fleet without a clear plan to replace them.

The letter was led by Senators Roger Wicker, the top Republican on the Senate Armed Services Committee, and Susan Collins, the top Republican on the Senate Appropriations Committee.

They said Biden should make an “AUKUS-specific” spending request along with a multi-year plan to increase US submarine production to a minimum of 2.5 Virginia-class attack submarines per year, compared with the 1.2 such submarines currently being produced.

The Virginia class submarines were designed by General Dynamics Electric Boat and Huntington Ingalls Industries.

The multi-stage AUKUS project announced in March was intended to deliver three US Virginia-class nuclear-powered subs to Australia in the 2030s, with the UK to then build and deliver a new nuclear submarine, which would then be built in Adelaide from 2042.

The project was expected to cost Australian taxpayers up to $368 billion.

Big questions remain, however, over issues including US curbs on the extensive technology sharing needed and how long it will take to deliver the Virginia-class submarines, given limited US production capacity, even as the perceived threat posed by China that inspired the project mounts.

-with AAP