Three British crew members and one Australian were hurt on board the vessel which is currently 400 miles off the California coast in the Pacific Ocean.

They suffered a range of injuries – including suspected broken ribs – when a wave hit the boat in storm conditions yesterday, sweeping away its steering wheel and mount and some of its communications equipment.

The boat, the Geraldton Western Australia, is one of 10 UK-registered 68ft yachts competing in the Clipper Round The World Yacht Race, which takes place once every two years.

Race organisers Clipper Ventures said the injured crew include Jane Hitchens, a 50-year-old doctor from Kent, who has four suspected broken ribs, and Mark Burkes, 37, from Worcestershire, who has suffered a back injury.

The others were named as Nik Brbora, a 28-year-old software engineer living in London, who has possible pelvic sprain, and 62-year-old Max Wilson, from Queensland, Australia, who has two suspected cracked or broken ribs.

The rest of the 18-strong crew are said to be uninjured but shaken by the incident and those who are medically-trained have treated the four injured crew members.

An attempt was made at around 2am last night (6pm local time) to parachute medical help to the sailors but it was abandoned after poor weather conditions meant paramedics were unable to jump out of the aircraft.

A helicopter will now be sent to help. At around 4pm this afternoon (8am local time) it will launch from a coast guard ship to deliver medical supplies. Subject to their medical condition, the injured crew will be taken off the yacht.

Explaining the revised plan, US coast guard spokesman Levi Read said: "The coast guard rescue co-ordination centre diverted the coast guard cutter Bertholf, and that cutter is making its way towards the vessel.

"The coast guard also launched a long-range helicopter to rendezvous with the Bertholf. Once it's in range the helicopter will be able to take off from the ship and fly to the vessel.

"They will then lower an emergency medical technician from the helicopter on to the boat.

"He will assess the injuries, treat them and if necessary evacuate the injured people and take them aboard the helicopter to the nearest medical resource."

Waves near the yacht are reported to be between 9ft (2.7m) and 15ft (4.6m), and wind speeds are between 20mph (32km/h) and 30mph (48km/h), he said.

Mr Read added: "It's certainly dangerous out there. But that kind of weather is normal for this time of year especially for the storms we've been having here in California."