The latest rotation of US Marines has touched down in Darwin as they prepare to join Australian soldiers in training in “humanitarian assistance, security operations, and high-end live fire exercises”.

The 2500 member strong Marine Rotational Force-Darwin will spend the next seven months working closely with their Australian counterparts as well as other partner nations from around the region.

It comes on the back of last week’s announcement of the AUKUS nuclear submarine deal, and Deputy Prime Minister Richard Marles said the US continued to be Australia’s “most vital security partner”.

“Over the next six months, the Australian Defence Force and US Marine Corps will conduct a comprehensive range of training activities including humanitarian assistance, security operations, and high-end live fire exercises."

Secretary of Defense Lloyd Austin said Tuesday that the US will increase its military presence in Australia in a buildup aimed at China.

In a joint press conference with Australia’s defense minister and foreign minister, Austin said that the US will increase its rotational forces in Australia. “That includes rotations of bomber task forces, fighters, and future rotations of US Navy and US Army capabilities,” Austin said.

Many countries in the region are not eager to get on board with the US’s confrontational approach to China. The prime minister of Papua New Guinea said this week that his country can’t afford to get caught between the US and China and said he told the US your “enemy is not my enemy.”

Indonesia’s president expressed similar concerns during a meeting of the Association of Southeast Asian Nations (ASEAN) in November, saying the ASEAN must not let the region turn into a frontline for a new Cold War.

Details on the rotational deployments aren’t clear, but they will likely focus on the Australian city of Darwin in the Northern Territory, where US Marines have been rotating through for years.

The US will increase rotations of its air, land and sea forces to Australia and has condemned China’s “dangerous and coercive actions” across the Indo-Pacific region.

As part of the step-up in defence ties, the US plans to preposition munitions and fuel in Australia to support its military forces.

Airfields in northern Australia are set to be upgraded to enable rotations of US aircraft.

Defence secretary also pledges to help Australia acquire nuclear-powered submarines ‘as quickly as possible’ at annual high-level talks.

Austin said the US would “increase rotations of our air, land and sea forces” to Australia as the two countries were “determined to be a force for stability” in the region.

“That includes rotations of bomber task forces, fighters and future rotations of US navy and US army capabilities,” Austin said, adding that the specific details would be worked out by officials and announced at a later date.

The UK defence secretary, Ben Wallace, will join Marles and Austin for a first meeting of the Aukus defence ministers on Thursday.

The agreement was finalized during a joint U.S.-Australia meeting that included Austin and his defense minister counterpart from Canberra.

"Based upon today's talks, we will increase the rotational presence of U.S. forces in Australia," Austin said at a press conference at the State Department. "That includes rotations of bomber task forces, fighters and future rotations of U.S. Navy and U.S. Army capabilities."

The increased military presence in Australia comes after the U.S. and U.K. announced in September 2021 that they had agreed to school the Australians on the "extremely sensitive" technology of nuclear-powered submarines. The U.S. had previously shared the technology only with the British.

American submarines will visit Australia more regularly but Defence Minister Richard Marles has rejected basing them down under to bolster our defences until our nuclear-powered boats hit the water.

Mr Marles is planning to use this week’s first meeting of AUKUS defence ministers to lock in the key planks of Australia’s nuclear submarine plan before it is unveiled early next year.

But he said home-porting US submarines in Australia was “not the answer” to covering any capability gap that emerged before our boats were in service.

This week’s AUSMIN meeting between Australian and US defence and foreign affairs ministers is also likely to lock in an expanded US Marine rotation in Darwin, and potentially the deployment of more US aircraft including nuclear-capable B-52 bombers.