BEIJING: Relations between the Chinese and US navies are their "best in history" and exchanges between the two will become more systematic in the future, China's military on Friday cited the country's naval chief as telling visiting US officers.

The comments by navy chief Wu Shengli come as Washington considers conducting freedom-of-navigation operations within 12 nautical miles of artificial islands China has built in the disputed South China Sea, without saying when it would do so. Such a move would likely infuriate Beijing.

Both China and the United States had worked hard to increase military interaction, holding joint drills and agreeing rules on encounters at sea and in the air, Wu said, according to the official People's Liberation Army Daily.

"At present, relations between the Chinese and US navies are at their best time in history," Wu was cited as saying. "Exchanges and communications are more trusting and effective." This has not come easily though, and is the result of hard work by both sides, he added.

"In the future, exchanges between frontline forces from both countries will gradually become more systematic," Wu said.

There was no mention of the South China Sea.

Read: US, China trade barbs over rights violations

The US naval delegation Wu met earlier this week visited China's sole aircraft carrier. The military's newspaper said they also visited a submarine school and a command college.

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.

China turns over remains of US World War II fliers

China has handed over the remains of what are believed to be three American fliers killed in a plane crash in Tibet during World War II, state media reported Friday.

The ceremony in the city of Chengdu on Thursday was a reminder of the close cooperation between the U.S. and China's then-Nationalist government in the struggle against Japan.

The 28 human bones and a boot were found in and around the wreck of a C-87 transport plane that crashed in 1943 while flying over the Himalayas between China and India, the China Daily newspaper reported.

The remains are believed to be from members of the US military. The crash site was discovered in 1993 and the remains of five airmen previously were handed over to the US in 1999, the paper said.

The additional bones were found during an expedition to the remote site in August to recover parts of the aircraft for a museum. Between 1942 and 1945, US planes flying between Sookerating in the eastern Indian state of Assam and the Chinese wartime capital of Kunming delivered approximately 650,000 tons of supplies to China-based US forces and to Chinese Nationalist forces battling the Japanese.

High altitude, bad weather and aircraft failure made the journey hazardous, resulting in the loss of 594 aircraft along with 1,659 personnel. Many planes simply became lost, ran out of fuel and crashed into the rugged mountains.

Despite the history of joint struggle, the Communist's 1949 victory in the Chinese civil war forced the Nationalists to flee to Taiwan and set the stage for decades of mutual suspicion between Beijing and Washington.

That precluded any chance of cooperative searches for remains until the normalisation of diplomatic ties in 1979. While Beijing now again honors the wartime alliance, it remains locked in a struggle for military supremacy in Asia, particularly in the South China Sea where their forces operate in close proximity.

Even so, exchanges between the US and Chinese militaries have grown in both scale and depth. Earlier this week, a US Navy delegation visited China's first aircraft carrier and a submarine training base.