Britain touted its "historic" new treaty with Australia in a government statement but gave few details beyond saying it would help economic cooperation, and "underpin" the existing three-nation AUKUS pact.

"This historic Treaty confirms our AUKUS commitment for the next half century," said Defence Secretary John Healey, who is visiting Australia along with Foreign Secretary David Lammy.

A US defence official last month revealed that a review of AUKUS was underway to ensure it "aligned with the President's America First agenda" and that the US defence industrial base was "meeting our needs".

The British statement repeated previously released figures that the AUKUS submarine programme would lead to the creation of 21,000 UK jobs.

It said the submarine programme was expected to be worth "up to" 20 billion pounds (US$27 billion) in British exports over the next 25 years.

Under the 2021 AUKUS deal, Australia would acquire at least three Virginia-class submarines from the United States within 15 years, eventually manufacturing its own subs.

The US Navy has 24 Virginia-class vessels but American shipyards are struggling to meet production targets set at two new boats each year.

In the United States, critics question why Washington would sell nuclear-powered submarines to Australia without stocking its own military first.

Analyst Tom Corben from the US Studies Centre in Australia said the new treaty between Canberra and London was an important show of solidarity.

"The symbolism is important given everything else that is happening," he said.

Britain's defence and foreign ministers were visiting Australia as their country's Carrier Strike Group and 3,000 personnel took part in annual Talisman Sabre military exercises across Australia and Papua New Guinea.

"The UK-Australia relationship is like no other, and in our increasingly volatile and dangerous world, our anchoring friendship has real impact in the protection of global peace and prosperity," Lammy said.