The United States' increasing presence in the Asia-Pacific region is not meant to threaten China, a US national security official said on Tuesday, after US President Barack Obama's nine-day trip to the region.

"With regard to China, I think the president was very clear that we do not see our engagement in the region as any way coming at the expense of China," Ben Rhodes, deputy national security adviser for Strategic Communications, said during a video conference.

Rhodes said the stability that the US has provided in the region has contributed to China's successful and peaceful development.

Obama wrapped up a nine-day trip to the Asia-Pacific region on Nov 19, where he attended the Asia-Pacific Economic Cooperation leaders' meetings in Hawaii, visited Australia where he announced 2,500 Marines would be stationed in the country and attended the East Asia Summit in Indonesia for the first time.

Rhodes said part of US role in the region was to ensure "maritime security".

"We have a long-standing commitment to the region and a long-standing relationship to its allies and partners that we feel we need to deepen, so they are on a stronger footing for the 21st century," said Rhodes.

As it is withdrawing from Iraq and Afghanistan, the US wants to enhance its ties with its Asian allies, said Rhodes.

Obama's visit to Darwin, the capital of Australia's Northern Territory has "an important symbolism", said Walter Lohman, director of The Heritage Foundation's Asian Studies Center.

Darwin is on the northern coast of Australia, facing a region that includes the South China Sea and the East China Sea, Lohman said.

Rhodes said the US has pursued a program of military exercises with a number of countries in the region, which it plans to increase "from joint exercises to response to contingencies like natural disasters".

The US also wants to increase such capacity with China, he added.

His comment echoed Australian Defense Minister Stephen Smith's statement on Tuesday that Canberra would seriously consider trilateral military training with the US and China.

The trilateral drill was suggested by Indonesian President Susilo Bambang Yudhoyono following talks with Australian Prime Minister Julia Gillard at last weekend's East Asia Summit in Bali.

There has so far been no response from the Chinese government but Niu Jun, an international relations professor at Peking University, said it is "not impossible", noting that the US and Chinese navies have held joint search-and-rescue drills.

Rhodes also stressed that part of the "context of the US presence" is "dialogue with China and dialogue with the PLA" to build trust between the two nations.

Trust is precisely what the US and China urgently need to work on, strategists on both sides of the Pacific have repeatedly said, including Henry Kissinger, the architect of US-China relations, who said strategic trust between the US and China is critically important in times of difficulty.

The real problem that complicates bilateral relations is that both sides lack an understanding of each other's strategic intentions, according to Niu.

"US policymakers tend to think the decision-making process in China is highly opaque and its policy is highly unpredictable. China, too, suspects US' moves as 'containment'," said Niu.

Niu dismissed the belief that China, as a rising power, and the US, as an incumbent power, play a "zero-sum" game in the region.

"People across the Pacific were preoccupied by the possibility of conflicts in Taiwan about 10 years ago, but now the Chinese mainland holds large accounts of the US debt and US invests so heavily in China," Niu said.

"The region is big enough to accommodate the two powers' interests," he said.