A seriously ill American crewman aboard a yacht racing deep in the Southern Ocean is believed to have a blocked intestine, an Australian rescue official said yesterday.

An Australian airforce surveillance aircraft plans to rendezvous at first light today with the yacht in the round-the-world Volvo Ocean Race and drop urgent medical supplies.

Keith Kilpatrick, a 40-year-old sail trimmer on New Zealand skipper Grant Dalton's Amer Sports One, has a serious stomach problem and is being treated with morphine by a doctor on board, Volvo Ocean Race office said in a statement.

"Kilpatrick is currently receiving antibiotics and morphine and is on a saline drip and the boat's limited medications are now running out," the race organisers said.

The yacht is around latitude 47 degrees, 41.40 minutes south and out of range for a helicopter evacuation.

A spokesman for the Australian Maritime Rescue Co-ordination Centre said it had been notified Kilpatrick had "a suspected blocked intestine" and could not keep fluids down. An Australian airforce PC3 Orion long-range surveillance plane from Australia's southwest coast is not expected to reach the yacht until early today. "They will drop supplies, but they have to do it during daylight hours," said the rescue centre spokesman.

Kilpatrick has been a professional sailor for 20 years, competing in eight long Pacific races and the 1992 US Olympic trials.

Currently sixth in the second leg between Cape Town and Sydney, Amer Sports One is around 1,500 nautical miles southwest of Australia around the remote Kerguelin Islands.

Weather conditions in the area are wild with yachts being battered by four- to five-metre seas, persistent rain and winds gusting around 35 knots. Air temperatures are below zero and sailors are forced to wear goggles while on deck.

"Conditions are becoming heinous and forecast to get worse," said navigator Mark Rudgier on Assa Abloy, which is third.

Race officials said Amer Sports One was in a "fast lane" and gaining on yachts in front headed straight towards Australia. The yacht is the only boat in the eight-strong Volvo fleet with a doctor on board, navigator Roger Nilson.

Race officials said they had taken precautions in plotting the race course through the treacherous Southern Ocean to ensure rescue facilities were within reach of yachts.

"Prior to the start of this race the Volvo Ocean Race committee worked with the Australian Rescue Centre to bring the course within 2,000 nautical mile maximum range of rescue facilities," said race director Michael Woods.

Australian maritime rescue authorities have been called on to rescue several around-the-world sailors in the Southern Ocean.

British sailor Tony Bullimore spent four days inside his upturned yacht, in the same area as Amber Sports One, after it lost its keel during the 1997 Vendee Globe race.

An Australian navy frigate eventually reached Bullimore and rescued him from the freezing waters, along with fellow competitor Frenchman Thierry Dubois.

In 1994 solo French yachtswoman Isabelle Autissier was winched from her stricken yacht after it was hit by a freak wave in the Southern Ocean and drifted for four days.