A US naval delegation toured Beijing's sole aircraft carrier the Liaoning, Chinese media reported Wednesday, as friction increases between the two powers over territorial claims in the South China Sea.

Washington has said it may soon sail warships near Beijing's artificial islands in the area, challenging Chinese claims to a region through which as much as one-third of global oil shipments pass.

The US has challenged Chinese assertions that the installations are primarily for civilian uses, saying that they pose a threat to freedom of navigation and calling on the Asian giant to build trust through increased military transparency.

The visit of 27 US captains to China's largest warship was just such a move, according to a Wednesday editorial in the Global Times, a newspaper affiliated with China's ruling Communist Party.

The tour was "a good step which displays China's sincerity in military exchanges with the US and China's military confidence," it said, but added that Beijing should decrease opacity at "its own pace".

Participants discussed issues ranging from personnel training to "aircraft carrier development strategy" and joined their colleagues for a ship-board banquet, according to a report on China Military Online, a website affiliated to the People's Liberation Army.

Chinese naval officers visited the US in February, the article noted, as part of an annual exchange.

Despite tensions, the US has been keen to improve relations with China's armed forces, and China has largely been willing to satisfy US curiosity about the Liaoning, commissioned in 2012.

Former US defence chief Chuck Hagel toured the vessel last year during an Asian trip that included a stop in Japan.

The ship is China's first and so-far only aircraft carrier, the most visible symbol of its efforts to build a "blue water" navy, capable of projecting power beyond its near shores.

Built on the overhauled shell of a Ukranian carrier purchased in the late 1990s, it currently serves as a training tool, preparing Chinese military personnel to operate a future indigenous model, believed to be currently under construction.