The US Seventh Fleet commander said Wednesday he was not worried about a major conflict in Asia but about small incidents with unpredictable consequences in areas such as the South China Sea.

Vice Admiral Scott Swift said military-to-military dialogue between Washington and Beijing was taking place at the highest levels of command and both sides shared a desire to minimise tensions.

"I think we are in a very positive place with China and the vectors are moving in the right direction," he told reporters in Hong Kong, where the USS George Washington aircraft carrier was making a visit.

"We need to be as transparent as we possibly can."

But he said areas such as the potentially resource-rich South China Sea, where several countries including China have territorial and maritime claims, required special attention to avoid dangerous flare-ups over minor incidents.

"In general terms I'm concerned about any tactical trigger with strategic implications," the commander of the US Pacific fleet said.

Swift said the Association of Southeast Asian Nations had made "significant progress" in encouraging dialogue between the rival claimants to the sea, which stretches off China's southern coast into vital sea lanes.

"There's not much that keeps me up at night and I'm not worried about a major conflict breaking out anywhere in the region," he said.

"I do have concerns about a specific brush-up that could result in a tactical miscalculation, but I think rapidly compromise will prevail and those incidents will be appropriately adjudicated at the diplomatic level."

Beijing says it has sovereignty over essentially all of the South China Sea, a key global trading route. Its claim to the Spratly archipelago competes with those of Vietnam, the Philippines, Taiwan, Brunei and Malaysia.

China and Vietnam also have a long-standing dispute over the Paracel island group. A Vietnamese diplomat last week said the region was "rife with smoldering tensions that threaten to escalate into full-scale conflicts".

The Philippines and Vietnam have complained of increasing harassment of their fisherman by Chinese vessels in the region, while Taiwanese lawmakers have proposed deploying advanced missiles to the contested waters.

Swift's visit to Hong Kong, the autonomous southern Chinese harbour city formerly ruled by Britain, comes as Washington talks up Asia's strategic importance to the United States.

In his first trip to the Asia-Pacific region since taking over at the Pentagon, Defense Secretary Leon Panetta said last month that the United States wanted to strengthen its presence in the Pacific.

The United States will host the Asia-Pacific Economic Cooperation summit in Hawaii this week and Obama will attend the 18-nation East Asia Summit in Indonesia later this month.

Along with recent arms sales to Taiwan, Sino-US tensions have flared lately over alleged Chinese cyber spying and the sale by Chinese firms of counterfeit electronics that ended up in US military hardware.

There have also been reports that China has deployed four new nuclear-capable ballistic missiles, but Swift said he was not concerned by one particular strike threat or another.

"I would classify my view as being interested but not overly fascinated" by the reports of new missiles, he said.

He also played down a media report at the weekend saying China had acquired a space tracking station in Australia, a close US ally which also hosts and jointly operates a strategic US space tracking station called Pine Gap.

"That's not something that I wring my hands over," Swift said, adding it was normal for China to have "interests around the world".