Senior US officials say they are in talks with a "variety" of other countries about potentially involving them in the second phase of the AUKUS agreement.
Key points:
- White House Indo-Pacific coordinator Kurt Campbell said other allies could potentially take part in the second phase
- He did not name which countries the US has been talking to, however Canada and New Zealand have previously expressed an interest
- In the meantime, officials say the US is not underestimating challenges ahead for the delivery of nuclear subs in first phase
Australia will obtain nuclear-powered submarines under what's known as Pillar One of the deal with the United States and the United Kingdom.
Pillar Two will see the three nations working more closely together on other types of defence capabilities, such as artificial intelligence and quantum technologies.
White House Indo-Pacific coordinator Kurt Campbell said he expected there would be some areas where other allies and partners could also take part.
"That might be in hypersonics, that could be in cybersecurity, it could be in anti-submarine warfare," he told an event hosted by the Center for Strategic and International Studies think tank in Washington.
"I think the key is going to be … what do you bring to the table, and are you able to do it in such a way that is going to be practical and operational?
"So we're not just looking for theoretical applications and partnerships, but practical, real efforts that will enhance defence capabilities."
The remaining two members of the Five Eyes intelligence alliance, Canada and New Zealand, have previously expressed an interest in joining Pillar Two.
Dr Campbell did not name the countries being spoken to but said there were a "variety" of nations interested.
A report recently published by the US Congressional Research Service suggested Congress could consider directing the Defence and State Departments to expand Pillar Two, adding some analysts had argued that Japan should also be included.
"Congress may weigh the potential benefits, such as new members' capability and capacity, against the potential drawbacks," the report said.
"The latter may include the risk of administrative inefficiencies, negative impacts on US firms (e.g. through increased competition with foreign companies for US defence contracts), and geopolitical blowback (i.e. provoking a destabilising response from regional competitors such as China)."
US not 'underestimating' challenges still facing AUKUS plan
Pillar One of the AUKUS agreement will involve Australia purchasing a number of American Virginia-class submarines, before building new subs based on a British design using US technology.
The plan still needs to clear a number of legislative hurdles in the US Congress.
Questions have also been raised about how the Virginia-class submarines will be delivered to Australia, given the pressure US shipbuilders are already facing to produce enough new subs for the US Navy.
"It's too early to give you an answer on precisely where those submarines will come from," US Chief of Naval Operations, Admiral Michael Gilday, told the same event.
"Whether that's excess capacity or whether that comes out of US inventory."
Admiral Gilday said the US was ramping up its shipbuilding capacity and that there was close consultation taking place with members of Congress.
"I guess in short, we do not underestimate the difficulties that lie ahead," he said.
China has criticised the AUKUS pact, accusing the three partner countries of travelling "further down the wrong and dangerous path".
Dr Campbell said Australia and the UK had made a "fundamental decision" to strategically align with the US "into the distant future".
"It was not very many years ago that, if you had to make an argument [about] which countries might be prepared to reorient more closely with other countries in the region, like China, Great Britain and Australia were two countries that … flirted with different kinds of orientations," he said.
"And that period has changed fundamentally."