The US Coast Guard suspended its Pacific Ocean search for star Chinese sailor Guo Chuan, it said, after rescuers boarded his drifting yacht and confirmed he was not there but found his lifejacket.

Guo "was a professional mariner with a deep passion for sailing", the Coast Guard's Captain Robert Hendrickson said in a statement on Thursday Chinese time.

"Our deepest condolences go out not only to his family and friends but also to his racing team and the sailing community."

Footage released by the US Coast Guard showed Guo's 97-foot trimaran Qingdao China drifting across the waves hundreds of kilometres west of Hawaii, its red sail emblazoned "Peace and Sport".

During two days of searches over around 12,000 square kilometres both a US Navy helicopter crew and a Coast Guard Hercules aircraft overflying the vessel had been unable to contact Guo, it said.

Guo, by far the country's biggest sailing star, became in 2013 the first Chinese sailor to complete a non-stop solo circumnavigation of the globe.

The 51-year-old set off from San Francisco on October 18 in an attempt to set a record solo crossing of the Pacific, but his team lost contact with him on Tuesday afternoon Beijing time.

They alerted US authorities, and rescuers from the USS Makin Island amphibious assault ship reached the Qingdao China on Thursday Beijing time.

"The boat crew confirmed Chuan was not on the vessel although his life jacket remains aboard," the Coast Guard statement said.

They lowered the mainsail and left the Qingdao China -- originally built as the Idec 2 for French yachtsman Francis Joyon -- at sea, it added, saying his racing team was arranging to salvage the vessel.

On a verified Weibo social media account Guo's team said his personal items had been recovered.

In a sailing diary entry for October 20 posted by the team he said that listening to a recording of his two sons' laughter on his computer was "the world's most beautiful song, the song that puts me most at ease".

Guo had previously said that his greatest fear was to fall in the water, China's official Xinhua news agency reported, citing him as saying: "I fear being separated from the ship when I am sailing solo."

If he was to be thrown into the sea, he said, "I would never catch up with the ship. My chance of survival would be none."

- Eternal rest -

What happened to Guo remained unclear.

Guo's team said they had observed his speed slowed on Tuesday and attempted to contact him, but he did not answer either satellite calls or internet communication.

The US searchers had found a broken sail in the water, they added.

The US Coast Guard said it was called when Guo's team had not received notification from him for 24 hours.

The sailor had previously been "in constant contact" with his shore team and family and was "not likely to miss scheduled calls", it added.

Chinese fans expressed fears for the mariner, with one writing that it was "likely he was adjusting or repairing the sail when he was struck or an accident occurred and he fell".

Others urged rescuers to continue the search.

"Absolutely do not stop the search and rescue! It's only 24 hours, the water is warm enough, Guo Chuan's physical abilities are fine, if money's an issue the shore team must immediately open a donation account... You can't give up!"

But a tone of mourning and tribute also appeared, with one writing that sailors, like mountain climbers, embraced challenge to access a vast perspective, with "captains' hearts always facing the sea".

The writer added: "To rest eternally in the Pacific now, that's a respectable fate!"

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