Washington has launched a new trilateral security partnership with London and Canberra which will support Australia’s plan to build a fleet of nuclear-powered submarines, a move that will strengthen the allies’ ability to counter China.

The move is US president Joe Biden’s latest effort to bolster alliances amid increasing tensions with China over disputes ranging from the South China Sea to Taiwan.

Biden was preparing to announce the deal in a virtual event with Boris Johnson, UK prime minister, and his Australian counterpart Scott Morrison on Thursday evening in Washington.

The leaders said they would boost co-operation in areas such as cyber, artificial intelligence, quantum computing and undersea capabilities — in addition to helping Australia build a nuclear-powered submarine force.

One British official said the alliance would focus on maritime and defence technology, in contrast to the “Five Eyes” arrangement through which the US, UK, Australia, New Zealand and Canada share intelligence.

A senior US official said Biden did not tell China’s Xi Jinping about the initiative when the two leaders spoke last week. The new alliance — dubbed AUKUS — has been formed one week before Biden is due to host the leaders of Japan, India and Australia for the first in-person summit of the “Quad” — a security grouping that is also designed to counter China and which Beijing has critically described as an “Asian Nato”.

The US official said that while Australia would acquire nuclear-propulsion technology — which the US has only shared with the UK — Canberra would not develop nuclear weapons.

Kori Schake, head of foreign and defence policy at the American Enterprise Institute, said the deal would send a strong signal to Beijing.

It is “an elegant message, a reminder to China that Australia has the technological capabilities and alliance relationships that they could become a nuclear power if the threat China poses becomes so severe”, she said. “It also strikes me as a good moment for the Biden administration to demonstrate its commitment to the security of its allies after the debacle of the US withdrawal from Afghanistan.”

The US official said the vessels would boost Australian naval capabilities because they were faster and more stealthy than conventional submarines.

The boats can also operate further from Australia, including in the South China Sea, and do not need to surface as frequently.

Australian media said Canberra would end an existing $90bn programme to buy 12 French-designed conventional submarines. The official said the allies would decide over the next 18 months how to build the fleet.

“This is a fundamental decision that binds decisively Australia and the United States and Great Britain for generations,” the US official said.

Richard Fontaine, head of the Center for a New American Security, said the submarines were a “big deal” that would not only give Australia better capabilities but would help Washington, particularly amid criticism that China is outpacing the US in building navy ships and submarines.

“The real measure of comparison is not China on one side and the US on the other. It’s China on the one side with the US and its allies on the other,” said Fontaine.

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