Deputy Prime Minister Richard Marles met with US Secretary of Defence Lloyd Austin and British Secretary of State for Defence Ben Wallace in Washington DC under the AUKUS pact announced by then-prime minister Scott Morrison in September 2021.

In a joint statement, they said the three nations "reiterated their shared commitment to the partnership and reviewed progress on identifying a conventionally armed, nuclear-powered submarine for the Royal Australian Navy".

The statement expressed confidence the leaders of the three countries would make an announcement early next year.

They also agreed plans for joint military exercises in 2023 and 2024.

Mr Marles said he was pleased the US had indicated it would not leave Australia with a capability gap while it waits for the nuclear-powered submarines, not slated to be built and operating until 2040.

"I've been articulating for some time now that dealing with questions of the capability gap would need to be part of the work we're undertaking," he told ABC Radio.

"We need to be looking at ways in which we can get our first nuclear-powered submarine as soon as possible, but to the extent there is a capability gap which arises, we need to have answers as to how to plug that in ... I feel confident we will be able to have those answers."

He said Australia was on track to deliver a plan on nuclear-powered subs and how they would be funded early next year.

"The optimal path is crystallising and we're pretty excited about it," he said.

Mr Austin said the need for AUKUS was becoming clearer by the day.

"More than ever, our three countries share a similar outlook on the key challenges and opportunities confronting our world," he said.

"AUKUS will enhance our shared ability to sustain peace and stability in the Indo-Pacific, and since creating this trilateral security partnership our defence forces, industries, and scientific communities have been hard at work."

Mr Austin said "great progress" had been made finding Australia's pathway to conventionally-armed and nuclear submarines across the last 15 months.

Mr Wallace said he was delighted Australia would join the "highly-capable club".

"We will do everything we can in our capability to help support you get that capability," he said.

"It also gives our alliance capability that you will need to stand strong, if people threaten us in the future."

Australian Associated Press