The racing team of a Chinese professional sailor who went missing on a mission to set a solo trans-Pacific world record is imploring the U.S. Coast Guard to resume its search for him.

In a post titled “Who can help us save Guo Chuan?” the team said Friday it was disappointed the search for Guo was suspended two days ago. It also said members had written a letter to the Coast Guard for help.

“We are deeply saddened by the decision to suspend the search and beg you to continue searching until there is confirmation that he has lost his last chance for survival,” the group wrote in the letter, according to the statement on its official social media page.

“Guo Chuan’s crew will assist regardless of cost, if you could just tell us what to do,” they said in the statement.

The search was suspended Wednesday after a Navy crew from the USS Makin Island went aboard Guo’s 97-foot trimaran about 620 miles northwest of Oahu and found only his life jacket.

The Coast Guard often receives requests from family and friends of people missing in the ocean but can’t resume the search unless there’s new information, Chief Petty Officer Sarah Mooers said.

“It’s incredibly sad and it’s unfortunate this happened,” she said. “We never like suspending a search. Unfortunately, after a certain point it becomes necessary.”

The last indication that Guo was aboard the vessel was Monday, she said. “Four days is a long time for something or someone to move adrift.”

Guo “was a professional mariner with a deep passion for sailing,” said Capt. Robert Hendrickson, who directed the Coast Guard’s search. “Our deepest condolences go out not only to his family and friends but also to his racing team and the sailing community.”

Lt. Ben Powers, the Coast Guard pilot who was air commander in the search, said waves, wind and darkness hampered the effort.

“It was pretty frustrating not to find him, not to hear him,” Powers said Thursday at Barbers Point Air Station in West Oahu. “The hardest thing we do is search for a person in the water, because it’s a huge ocean.”

Guo, 50, was the first Chinese person to sail around the world in 2013, according to his website, guochuanracing.com. He left San Francisco on Oct. 18 to challenge the solo nonstop trans-Pacific world record of 21 days.

Powers piloted one of the HC-130 Hercules planes that participated in the search. He said he spent hours scanning the ocean for Guo through 4- to 6-foot waves. There was no moon, he said, so illumination was low even with night-vision goggles.

Rescuers radioed Guo every 15 to 30 minutes, Powers said. There was no response.

“When the person’s in the water, basically the only thing above the water is the person’s head,” Powers said. “So that’s really what we’re looking for — something the size of a human head from an aircraft from 300 to 700 feet.”

Guo’s team said a company that operates helicopters for tourism in Honolulu has expressed its willingness to provide up to 10 helicopters for the search. It said they can travel only 310 miles without stopping and would need a ship to serve as a platform for refueling on the sea.

The team is in contact with commercial ships, but the nearest one is hundreds of miles away because Guo was taking a nontraditional route, it said.

Guo’s sailboat, the Qingdao China, is adrift, and its main sail has been taken down, the Coast Guard said. Guo’s racing team plans to recover the sailboat, the Coast Guard said.