Image caption Nyad was one of the greatest long-distance swimmers in the 1970s

US swimmer Diana Nyad has been forced to abandon her attempt to be the first person to swim from Cuba to Florida without the protection of a shark cage.

Ms Nyad, 61, stopped 29 hours into an expected 60-hour swim, CNN reported.

"I am not sad, It was absolutely the right call," she told CNN, which had a producer on a boat accompanying her on the 103 mile (166km) swim.

Ms Nyad failed in her first attempt to complete the crossing from Cuba in 1978, when she was 28.

She set off from Havana on Sunday with the aim of reaching Key West in the Florida Keys on Wednesday.

But the swimmer was struggling with shoulder pain, ocean swells and asthma before she was brought on board a vessel at about 12:45 (0445 GMT) on Tuesday.

Ms Nyad was vomiting as she was hauled out of the water.

The US and Cuba - two former Cold War adversaries - still have no formal diplomatic relations.

It took more than a year of negotiations to get both countries to allow the epic swim to take place.

It was a huge operation, with support boats carrying medical assistants, nutritionists and a shark protection team.

These included two kayaks paddling beside her the whole way equipped with underwater electrical shark shields.