A US warship began a week-long port call in China Monday, a moment of cooperation as the two Asia-Pacific powerhouses jockey for position in the disputed South China Sea.

The USS Stethem, a guided missile destroyer, arrived in Shanghai ahead of planned drills with the People's Liberation Army Navy that include communications exercises and a surface rescue simulation.

The ship's commanding officer, Harry Marsh, told reporters the visit was intended to "build mutual trust" between the two navies.

US sailors, he said, would learn about their counterparts' "maritime experiences, so that when we operate at sea we can do it safely, and we understand what they are doing and what we do".

The stopover comes shortly after the US sailed a warship near artificial islands being built by Beijing in the South China Sea.

Washington says the construction projects present a threat to freedom of navigation in the critical region through which passes one-third of the world's oil.

Beijing denies those allegations, saying they are a pretext for the US to flex its muscles as it "pivots" to the Asia Pacific.

The disagreement has become a major point of friction between the two countries, and threatens to become an issue at this week's Asia Pacific Economic Cooperation forum in the Philippines, where Beijing says it should not be discussed.

Nevertheless, Harris downplayed the friction: "Countries may have some disagreements, yet our navies are able to operate safely at sea."

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