U.S. President Barack Obama and Australian Prime Minister Julia Gillard on Wednesday, November 16, unveiled plans for a deepening of the U.S. military presence in the Asia-Pacific, starting with thousands of U.S. Marines operating out of a defacto military base in the Australian port of Darwin.

According to Reuters, U.S. troops in Darwin, only 820 kms (500 miles) from Indonesia, would be able to react quickly to any humanitarian and security issues in Southeast Asia, where disputes over sovereignty of the South China Sea are causing rising tensions.

"With my visit to the region I am making it clear that the United States is stepping up its commitment to the entire Asia-Pacific region," Obama told a joint news conference with Gillard in Canberra.

Deployment of an initial company of 200-250 Marines would begin in 2012 and expand to up to 2,500 eventually, Gillard said.

The move may be seen by Beijing as further evidence of Washington's attempt to encircle China, with U.S. bases in Japan and Korea and now troops in Australia.

"We hope that bilateral cooperation between the countries concerned will be of benefit to the peace, stability and development of the Asia-Pacific region," said Chinese Foreign Ministry spokesman Hong Lei.

Some Asian nations are expected to welcome the U.S. move as a counterbalance to China's growing power, especially its expanding maritime operations, and a reassurance that Washington will not scale back its engagement in the region due to a stretched U.S. military budget.