Australia will buy as many as five US nuclear-powered submarines and later build a new model with US and British technology under a plan to strengthen the AUKUS Western alliance across the Asia-Pacific against rising China, a US official said on Monday.

US President Joe Biden was hosting Australian and British prime ministers Anthony Albanese and Rishi Sunak on a US naval base in San Diego, California, to announce the plan.

Australia, which joined the newly formed AUKUS group with Washington and London 18 months ago, will not be getting nuclear weapons.

Biden's National Security Advisor, Jake Sullivan, told reporters flying on Air Force One to California that the submarine plan illustrated Washington's long-term commitment to guarding "peace and stability" in the Asia-Pacific region.

The partnership with Australia, which involves sharing secret nuclear technology previously only given to Britain, is "a decades-long, maybe a century-long commitment," Sullivan considered.

Three conventionally armed, nuclear-powered Virginia class vessels will be sold "over the course of the 2030s," with the "possibility of going up to five if that is needed," he indicated.

The new model, also nuclear-powered and carrying conventional weapons, is a longer-term project and will be dubbed the SSN-AUKUS, the US official highlighted. It will be built on the base of a British design, with US technology and "significant investments in all three industrial bases," Sullivan mentioned.

On Monday, Sunak's office said Britain is also moving to beef up its military capabilities. More than $6 billion in additional funding over the next two years will "replenish and bolster vital ammunition stocks, modernize the UK's nuclear enterprise and fund the next phase of the AUKUS submarine program," Downing Street announced.

Australia had previously been on track to replace its aging fleet of diesel-powered submarines with a $66 billion package of French vessels, also conventionally powered.

The announcement by Canberra that it was backing out of that deal and entering the AUKUS project sparked a brief but unusually furious row between all three countries and their close ally France.

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Compared to the Collins-class submarines due to be retired by Australia, the Virginia-class is almost twice as long and carries 132 crew members, not 48.

China warned that AUKUS risked setting off an arms race and accused the three countries of setting back nuclear nonproliferation efforts.

"We urge the US, the UK and Australia to abandon the Cold War mentality and zero-sum games, honor international obligations in good faith and do more things that are conducive to regional peace and stability," Chinese Foreign Ministry Spokesperson Mao Ning told reporters in Beijing.

Last week, Chinese President Xi Jinping made a fiery statement, accusing the United States of leading a Western effort at "all-round containment, encirclement and suppression of China."

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