The Pentagon's rebalance to Asia is on track, with 60 per cent of the United States Navy's warships set to be repositioned in this part of the world in the next three years, a top US Navy official said.

Another 21 warships will be added to the US Navy's armada policing Asia-Pacific waters as part of the country's shift to focus on this region, Seventh Fleet commander Joseph Aucoin told reporters at a media roundtable yesterday.

These ships will be based along the US West Coast and in the Pacific, and will patrol waters that include the South China Sea where China's rising military might has unsettled others in the region.

Vice-Admiral Aucoin, who took command last September and is attending this week's Singapore Airshow, said he is also asking US Coast Guard ships to be more involved in patrols, as China increasingly deploys its coast guard vessels in these waters.

China's territorial claims to several islands are contested by Taiwan and four Asean countries - Malaysia, Brunei, Vietnam and the Philippines. Beijing has also been reclaiming land, putting weapons on a reclaimed reef, and warning ships and planes from other countries away from the area.

Vice-Adm Aucoin said he was concerned about the "professionalism" of China's coast guard vessels and felt that getting them to abide by a code, which US and Chinese naval ships now follow to manage unplanned encounters at sea, "would be a good thing".

The Seventh Fleet has 80 to 100 ships and submarines, including the USS Ronald Reagan aircraft carrier strike group, covering a large swathe of water from Japan to India. In contrast, Beijing's South Sea Fleet operates 116 naval vessels and has more than 200 coast guard ships.

But Vice-Adm Aucoin said the relationship between the Chinese and US navies is "moving forward in a positive way", with senior officers from both sides meeting routinely. He also revealed that he will be taking the Seventh Fleet's command ship USS Blue Ridge to China this summer.

He also hopes to conduct more multilateral exercises that involve a wider range of countries, including Sri Lanka, Cambodia and Indonesia, to strengthen relationships across the region.

Vice-Adm Aucoin noted that while the US Navy shares a good relationship with Singapore and routinely deploys its ships here, it does not want to build bases or "additional infrastructure" here.

"We are satisfied with where we are at," he added.