The AUKUS announcement has fuelled more speculation about possible expansion of the marines' presence in the Top End, which Defence Minister Peter Dutton has already said he would like to see.

In an interview with the ABC, the USA's Charges d'Affaires in Australia, Michael Goldman, said talks on the subject were ongoing.

Michael Shoebridge, the director of defence, strategy and national security at the Australian Strategic Policy Institute, said northern Australia was becoming another staging point for US personnel, logistics and resources in the Asia Pacific.

Under the 2011 agreement, marines will keep returning to Darwin each dry season for 25 years, ending in 2036. The USA Charges d'Affaires, said the deployments were "just a beginning rather than an end" of the US presence in Australia.

Britain’s nuclear-powered submarines are to use Australia as a base so that they can have a more persistent presence in the Indo-Pacific region under plans discussed by ministers.

Senior government sources said that the AUKUS pact could lead to the Royal Navy’s £1.4 billion Astute-class attack submarines undergoing deep maintenance in the region so they can stay deployed for longer rather than returning to the Faslane naval base in Scotland.

The plans would materialise once the Australians start building their own fleet of at least eight nuclear-powered submarines over the coming years with the help of the British and Americans.

The source said that the trilateral pact announced last week “opens up opportunities” for the UK, adding: “You’ve got another base … if you want to have more of a persistent presence you need access to maintenance.”

James Peddell, a former defence technology attaché in Washington with experience in submarine technology, said that a base in Australia could allow UK submarines with conventional weapons to have a permanent presence in the region, and also enable cost-sharing between the allies.

A former Australian assistant defense secretary says there might be more Marines in Australia in the wake of a new trilateral defense alliance.

AUKUS, which officials had been talking about for the past 18 months, is about much more than submarines, Babbage said.

“We are going to see larger U.S. forces coming, including U.S. Army forces and air power coming here on rotation,” he said. “It’s quite likely the Marine Corps presence could be scaled up.”

The U.S. Embassy in Canberra and the Australian Defence Department did not respond Friday to questions about the possible effect of the trilateral defense pact on the Marine rotations.

About 2,200 US Marines expected in Darwin in the 2021 rotation as Canberra also eyes improved air, maritime capability.

Outlining further measures on a visit to Washington, Defence Minister Peter Dutton said on Thursday that Australia will be “significantly enhancing” cooperation including working together on the development of missiles and explosive ordnance.

He said Australia was willing to see more US Marines in a 10-year rotation through the northern city of Darwin.

“I do have an aspiration to make sure that we can increase the numbers of troops through the rotations,” Dutton said.

Australia's new strategic alliance with the United States and United Kingdom is likely to see more troops, war planes and naval vessels in the Top End. But any expansion could be hindered by the controversial lease of Darwin Port to a Chinese company, national security experts say.

Heralded as the most significant shift in Australia's defence direction in decades, the centrepiece of the trilateral security partnership, dubbed "AUKUS", is a plan to build a fleet of nuclear-powered submarines.

But Defence Minister Peter Dutton has also flagged a major enhancement in Australia's military cooperation with the US, which currently deploys about 2,500 marines to the Top End each dry season.

John Coyne from the Australian Strategic Policy Institute said the 99-year lease of the Darwin Port to Landbridge could prove an impediment to the allies' military expansion plans.