Rescuers sent by the US Coast Guard didn't see Chinese sailor Guo Chuan on his boat, Guo's shore team said on Thursday.

Guo Chuan's vessel is found about 620 miles northwest of Hawaii's main island of Oahu. [Photo provided to chinadaily.com.cn]

The Coast Guard used a helicopter to drop rescuers on Guo's trim ran floating on the Pacific Ocean.

Guo was last heard just after 15:00 Tuesday Beijing time when his boat sailed 900 nautical miles off the west of Hawaii. All attempts to contact the sailor had failed.

Wednesday Beijing time, Guo's vessel was found about 620 miles northwest of Hawaii's main island of Oahu. The airborne search team did not see Guo on deck, but the main lateen sail of the 97-foot trimaran was broken off in the water.

"It's hard to say how many percentage but it could be true that the mariner is onboard alive on the vessel," said Tara Molle, a spokesperson for Coast Guard Honolulu.

The Coast Guard sent an HC-130 Hercules, a long-range surveillance and transport aircraft, to the area where Guo's vessel was sending a location signal. The crew tried to communicate with Guo via wireless walkie-talkie, but failed.

Two rescue vessels have been sent by the US Navy and crews will access and board Guo's vessel to investigate, according to the Consulate-General of China in Los Angeles.

"It takes a couple of hours for our aircraft to arrive at that area, and way longer for the vessels," said Molle, adding that the aircraft crew had been working continuously since Tuesday afternoon local time except for refuels.

Guo set sail of his trimaran Qingdao China from San Francisco's iconic Golden Gate Bridge on Oct 18 for Shanghai hoping to set a new sailing world record for solo crossing.