The first batch of 2,500 US Marines to be deployed in Australia began work on Wednesday as Washington bolsters its presence in the Asia-Pacific to "seek a balance of power with China".

Some 200 Marines touched down in tropical Darwin overnight as part of an enhanced defense cooperation outlined during a visit by US President Barack Obama in November.

The troops are in the Northern Territory on a six-month rotational basis and will be based at Robertson Barracks on the outskirts of the city, building to some 2,500 by 2016-2017.

The Chinese Foreign Ministry had no response to the troop deployment as of press time on Wednesday. But ministry spokesman Liu Weimin said earlier that against the backdrop of a sluggish global economy and an international consensus and focus on promoting development, it is worth debating whether strengthening and expanding the US-Australia military alliance is appropriate and consistent with the common aspirations of countries in the region and the international community.

Geng Yansheng, spokesman for the Defense Ministry, in late November criticized the US' strengthened military pact with Australia, calling it a figment of "Cold War mentality" that will destabilize the Asia-Pacific region.

"Military alliances were created by history. We think that all moves to strengthen and expand military alliances are a product of a Cold War mentality that runs counter to the trend of peace, development and cooperation," Geng said.

In a joint statement, Australian Prime Minister Julia Gillard, Defense Minister Stephen Smith and Northern Territory Chief Minister Paul Henderson welcomed what they said was the latest chapter in a more than 60-year alliance with the US.

"It represents an evolution of existing exercises and activities that the United States already conducts with the Australian Defense Force in Australia," they said.

"The intent in the coming years is to establish a rotational presence of up to a 2,500 personnel Marine Air Ground Task Force, rotating into Northern Australia in the northern dry season.

"There are no (permanent) US military bases in Australia, and this will not change," they added.

The US military currently has only a limited deployment in long-standing ally Australia, including the Pine Gap Joint Defense Facility spy station near Alice Springs.

Gao Zugui, a researcher at the Research Institute for International Strategic Studies, said the US is trying to avoid losing power in the Asia-Pacific region.

Australia is a more loyal ally to the US than Japan and its other allies in the region, Gao said.

The US is not only enhancing alliances with traditional allies Japan, South Korea, Australia and New Zealand, but is also attempting to improve ties with other counties in Southeast Asia such as Myanmar, Thailand and Cambodia, Gao said.

But he doesn't think that the US is trying to become a leader in the Asia-Pacific region.

"The US is actually trying to avoid losing control of the Asia-Pacific region and achieve a balance of power with China in this region," said Gao.

China Daily-AFP