The UK's departing Chief of the Defence Staff has signalled the new trilateral AUKUS security pact with the United States and Australia could be expanded to include other allies such as Japan.

In a wide-ranging discussion at a Washington-based think tank, General Sir Nicholas Carter has reflected on the formation of the new military group which will work to develop a nuclear submarine fleet for Australia.

General Carter has told the Center for a New American Security he believes there are still some "question marks" about information sharing between the AUKUS partners.

"I think like all these things we're going to see how it goes – I mean I think there are some question marks about how we share information and those sorts of things," he said.

"I hope this could act as a catalyst for us all to be a bit more open-minded about how we share information with allies and partners because that would be helpful."

Asked whether countries like Japan feel excluded by the new partnership, General Carter suggested the nation could eventually join, along with remaining Five Eyes partners Canada and New Zealand.

"It's a first step in terms of industrial development between like-minded partners and I absolutely know that the architects of it reckon that if it could be made more inclusive, if there were opportunities there, then that's the direction of travel it would go."

"The same applies to Five Eyes (the intelligence sharing alliance of Australia, Canada, New Zealand, the United Kingdom and the United States) and also to other like-minded countries".

Government and diplomatic sources have played down the British general's comments, telling the ABC there are no plans for AUKUS to include any other nations.

During his appearance, the retiring Defence Chief also talked up the United Kingdom's growing military deployments to the Indo-Pacific.

General Carter said the presence of the Queen Elizabeth Carrier Strike Group in the region was "not going to happen every year", but said the UK intends to have two warships operating continuously and have a "littoral strike group from time to time" there.

At the end of November, General Carter will be succeeded as Chief of the Defence Staff by Sir Antony Radakin, a naval officer who was involved in the early discussions that led to the AUKUS agreement.