Earlier this week Icelandic radio reported that the star of the 1993 movie Free Willy was defying attempts to rehabilitate him to his natural habitat, more than a year after being airlifted to Iceland.

But the Ocean Futures Foundation has responded saying that Keiko could be set free as early as June next year.

Keiko beginning his journey back to freedom

Foundation president Jean-Michel Cousteau added that Keiko had shown "a big ability to adapt and had very well acclimatised himself to living in the sea".

Killer whales can only survive in groups but, according to Icelandic radio, Keiko had shown little interest in interacting with his counterparts in the wild.

This has been denied by Ocean Futures who say that, on the contrary, Keiko was making good progress in this area.

Other signs of improvement noted included the increasing length of time the whale now spends underwater and away from humans.

The next stage of the Keiko's return to the sea is being planned by the foundation.

It involves putting up a net across part of the Westman Islands, where Keiko is being kept in a tank.

This will allow his trainers to take him for "walks" to reintroduce him to nature.

However, the foundation has admitted that the process to reintegrate Keiko with his natural habitat had proved long.

Campaigners feared Keiko would go belly-up in captivity

It added that reports that the animal was still unable to catch his own fish were correct, but that this behaviour was normal.

Keiko, whose name means "Happy Boy" in Icelandic was captured in waters off Iceland in 1979.

After a spell in a local zoo, he travelled to Canada and Mexico before appearing in the hit film.

A year later, a Life magazine article highlighted the "unacceptable" conditions he was being subjected to in an aquarium Mexico.

Following a $4m donation from Free Willy's makers, Warner Bros, moves to release the whale were boosted.

Eventually in 1998, Keiko was flown back to Iceland and put in the care of Ocean Futures who, if all goes to plan, could soon be bidding him a bitter-sweet farewell.