Mike Plant.

The 41-year-old, who has sailed around the world three times, was still missing last night after four days of scanning the Atlantic 600 to 1,000 miles northeast of Bermuda.

The Navy joined the search as a result of "high-level talks'', US Coast Guard spokesman Petty Officer David Silva said.

It is believed there were attempts to bring in the Portuguese naval units based in the Azores as well, but it was reluctant to join the effort unless presented with further facts on Mr. Plant's apparent disappearance.

Mr. Silva said two C-130 planes will go out searching again today at the crack of dawn, joined for the first time by two P-3 Orions.

As the search planes have been operating out of Bermuda, it is likely the Orions will be those based at the US Naval Air Station.

"We have searched up to 120,000 square miles of ocean so far and we haven't found a thing,'' Mr. Silva said.

Mr. Plant's venture and his custom-designed yacht Coyote were featured in this month's edition of Sailing World .

Mr. Sean McNiel, an editor at the magazine and good friend of Mr. Plant's, called the situation "depressing''.

He said Mr. Plant's fiancee was waiting anxiously for news in Jamestown, Rhode Island, where the couple live. He did not want to speculate on what might have happened.

The article said Coyote was likely to be one of the most "radical'' in the Vendee Globe Challenge fleet, with extremely low freeboard and a deep-draft bulb keel.

Designer Rodger Martin is quoted as saying the yacht would be "harder on the skipper...but we determined that Mike would just have to work himself up to it.'' Mr. Plant set out on October 16 from New York to France for the start of an around-the-world race. He was due in Les Sables d'Olonne on October 30.

The last contact with Mr. Plant is believed to have been a beacon signal picked up on October 27 by the Canadian Coast Guard, who took no action because it was too weak.

Because Mr. Plant had not registered his EPIRB device, the Canadians were unable to find out his name or nationality.

The search began last Friday when worried friends of Mr. Plant's reported he was more than two weeks overdue in France on a solo Atlantic crossing.

They helped trace the EPIRB distress signal received by the Canadians to Mr.

Plant.