But the pact is increasingly focused on developing advanced capabilities such as long-range precision firing, artificial intelligence and hypersonic weapons.

Wormuth said Australia could be the platform to test these weapons.

‘Dangerous precedent’: Aukus nuclear sub loophole causes proliferation fears

“One thing Australia has in spades is long distances and relatively unpopulated land,” she said in a telephone interview from Washington.

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“A challenge for us in the United States when it comes to hypersonics or even some of our things like the precision strike missile – which is not a hypersonic weapon but has very long ranges in some of its increments – for us to find open spaces in the United States where we can actually test these weapons, it’s a challenge,” Wormuth said.

“Australia obviously has a tremendous amount of territory where that testing is a little bit more doable – so I think that’s a unique thing, as an example, that the Australians bring to the table.”

US Secretary of the Army Christine Wormuth, centre, with senior US and Australian military officials. Photo: US Army/AFP

China has denounced the Aukus pact as undermining peace in the region – a charge that the US, Australia and Britain reject.

But critics have also asked whether it is truly cooperative, or whether the US, because of its size and overwhelming military power, will dominate.

Wormuth said she expected the two smaller partners to pitch in and “have skin in this game – and they do”.

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“The sense I got certainly from talking to senior Australian officials is they’re not doing this to make us happy, they’re not doing this just for fun,” said the Pentagon official, who visited Australia last week for the Talisman Sabre multinational military exercise.

“They’re doing this because they see it as in their own national interest in terms of being able to meet the different challenges that they see in the theatre.”

Australia ‘confident’ on getting subs as US attacks China’s Pacific ‘bullying’

Facing Russia’s war in Europe, threats from North Korea and a more bellicose China, the US has sought to bolster its defence alliances and put more advanced capabilities into the hands of allies like Australia, Ukraine and Taiwan.

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For much of the Cold War, it was Washington’s policy to be able to fight two major wars at once.

Wormuth admitted that today, budget constraints, US public opinion and the relative strength of Russia and China make such a doctrine impossible.

“I think there is a recognition that when you look at the size of our military, when you look at the size of the defence budget that the American taxpayer is willing to pay for, we … don’t plan to fight more than one major war at a time,” she said.

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Instead, the US hopes its alliance and nuclear arsenal will “discourage opportunistic aggression”.

“Given the sophistication of the Russian military and the Chinese military today, to try to size our military to hypothetically handle two wars at a time would be prohibitively expensive”.

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