US President Barack Obama will use a visit to Australia next week to announce that America will station Marines in Darwin, ministers indicated Friday, in a sign of heightened concern about China.
The Sydney Morning Herald said that the new permanent military presence had been under consideration for some years as Washington looks to boost its Pacific Command, and senior Australian politicians did not deny the plan.
The US currently has only a limited deployment in longstanding ally Australia, including the Pine Gap Joint Defence Facility spy station near Alice Springs, and the move represents a potentially significant geo-strategic shift.
"It is important to wait for the president to visit Australia and for him and the prime minister to confirm what further defence cooperation arrangements we may have planned," said Australia's Foreign Minister Kevin Rudd.
He added: "It has always made national security sense to have a strong security alliance with America."
Pentagon spokesman George Little declined comment, saying only: "Australia is an American friend and ally, and we will continue to work together to foster even stronger military ties with one another."
Obama arrives on Wednesday, visiting the capital Canberra before becoming the first US president to travel to Darwin in the north.
The US will not be building a new base in the city, but instead will reportedly use the existing Robertson Barracks nearby.
The facility is currently home to some 4,500 Australian soldiers and will need to be expanded to cater for the US Marines, the paper said, citing sources who declined to detail how many troops or sailors would be rotating through.
The plan would intensify the 60-year military alliance between the two countries, which has played a crucial part in anchoring the American influence in Asia.
In a speech to a national security workshop Friday, Defence Minister Stephen Smith said: "This would potentially see more ship visits, more visiting aircraft and more training and exercising through northern Australia."
It would also include "the pre-positioning of United States equipment in Australia", he added.
US Marines are already based at Okinawa in Japan and on Guam as America's chief combat force in the Pacific theatre, and analysts said the Australian move was largely a response to the rise of China.
Beijing is boosting its military spending and capabilities, and becoming increasingly assertive on the high seas where it claims sovereignty over essentially all of the South China Sea, a key global trading route.
"China looms very large for both Australia and the US," said Professor Geoffrey Garrett, chief executive of the US Studies Centre at the University of Sydney, adding that the US strategy had two elements.
"The first concerns strengthening America's alliances and friendships in the region as an insurance policy that China's until now very peaceful rise changes course," he told AFP.
"The second is trying to build a regional economic architecture for the Asia-Pacific based on the market principles of America and Australia that China over time will have powerful incentives to join, even if this entails domestic reforms it has been unwilling to undertake up until now."
Asked about the US potentially stationing troops in Australia, Chinese foreign ministry spokesman Hong Lei said Beijing had noted the reports.
"We hope that bilateral cooperation between relevant countries will be conducive to peace and stability of the Asia-Pacific region," he said.
Andrew Shearer, the director of studies at the Lowy Institute for International Policy, said the move was "not all about China".
"Everyone draws the China connection but it's as much to do with the rise of India as well," he told AFP. "It's not all about defence, but to be able to conduct disaster relief, counter piracy and keep shipping lanes free."