BEIJING (REUTERS) - Senior United States naval officers visited China's lone aircraft carrier this week, China's military said, as the two powers try to maintain military ties despite mounting tensions over Beijing's claims in disputed waters in the South China Sea.

The visit by the 27-member delegation of US naval captains to the Liaoning, a refitted former Soviet carrier, came as Washington considers sailing warships through international waters claimed by China, a move that would infuriate Beijing.

The US captains exchanged views with Chinese peers on topics like "personnel training and management, medical support and aircraft carrier development strategy", the Chinese navy's official microblog said late on Monday (Oct 19).

The visit was not covered widely in Chinese media until Wednesday (Oct 21).

On Tuesday, the US delegation visited the Chinese navy's submarine school, the microblog said, part of what was a reciprocal visit for a one-week trip to the United States by Chinese naval officers in February.

China-US relations have become increasingly strained over Beijing's territorial claims in the South China Sea, through which $5 trillion in ship-borne trade passes every year. Vietnam, the Philippines, Malaysia, Taiwan and Brunei also have claims in the area.

Washington is considering conducting freedom-of-navigation operations within 12 nautical miles of artificial islands China has built in the sea, without saying when it would do so.

Former US Defense Secretary Chuck Hagel made the first official foreign visit to the Liaoning in 2014, a move seen at the time as an attempt at transparency by China's military.

Even so, little is known about China's aircraft carrier programme, which is a state secret.

Chinese state media have hinted new vessels are being built, and the Pentagon, in a report earlier this year, said Beijing could build multiple aircraft carriers over the next 15 years.

The vessels are crucial elements in China's development of an ocean-going "blue water" navy capable of defending the growing interests of the world's second-largest economy as it adopts a more assertive stance in maritime disputes.