Wellington  - A rescue operation was launched Monday to save two Italian sailors stranded on a crippled yacht in the middle of the Pacific Ocean, about halfway between New Zealand and Chile.

An oil tanker was diverted to their aid, but New Zealand's Rescue Coordination Centre said it was 800 nautical miles from the 10-metre yacht and would not reach them for nearly three days.

They were identified as father and son, Pietro Fresi, 64, and Vittorio Fresi, 34, who reportedly sailed in their yacht Onitron from Italy in September planning to retrace the clipper route of sailing ships in the 19th century on a voyage expected to take up to 300 days.

The pair used a satellite phone to tell contacts in Rome that their yacht's mast had broken and was hanging over the side of the boat, and it had lost engine power about 3,000 kilometres from New Zealand.

New Zealand authorities, who have international responsibility for maritime rescue operations in the area, were alerted and they asked the oil tanker Hellespont Trooper to help.

Dave Wilson, of the Rescue Coordination Centre, said it was the nearest ship to the stricken yacht, but it would not reach it until about midnight New Zealand time (1200 GMT) on Wednesday.

Wilson told Radio New Zealand the yacht capsized in a storm in the early hours of Monday and although the sailors were able to right it, the mast broke in winds up to 45 knots and 7-metre sea swells.

"They are in quite good spirits considering and they will just hunker down and wait for that ship to arrive," he said. "They are inside the hull of the boat and just riding out the worst of the conditions now.

"It is quite amazing that they managed to come through unscathed."

Wilson said the weather was forecast to improve and the men had a life raft, 10 days of food and a distress locator beacon if they lost the satellite communication that had enabled them to keep in regular contact with New Zealand and the tanker.

Once the Fresis are found, the Hellespont Trooper is expected to take them to Argentina. (dpa)