A whale expert says there is only one way to cure Keiko the killer whale of his habitual hanging out with humans -- and that's to "kill Willy."

Nils Oien, of Norway's Institute of Marine Research, says Keiko's appearance this week in a fjord, where he swam with children, proves that the $20 million program to free the star of the Free Willy movies has failed -- and the child-loving cetacean must be put to sleep. 

"Those who believe that they are helping Keiko by setting him free are really doing the opposite," Oien told Norwegian reporters. 

"First, they spend millions on taming him and turning him into a movie star. Then they spend more millions on turning him back into a wild animal. 

"They should have let him live and die in captivity. Now . . . they should put him down." 

Oien's view has outraged the U.S. scientists who for more than seven years helped the Keiko's transition to life among his orca brethren. 

"We think it's absolutely absurd and completely shortsighted -- and coming from someone who just wants publicity for publicity's sake," said Nick Braden, a spokesman for the Humane Society of the U.S. 

"This person doesn't know what's going on," added David Phillips of the Free Willy Keiko Foundation. 

He said that Keiko looks strong and healthy, proving he has been prospering in the wild. 

"He's swimming miles across the ocean. He's associating with other orcas. He's on a positive track." 

Both Phillips and Braden's groups were monitoring Keiko as he continued to swim yesterday in the Skaalvik Fjord near Halsa, Norway, where he has been since last weekend. 

They conceded that it's bad for him to associate with humans -- but his return to shore does not show that Willy would rather not be free. 

"I really think that, ultimately, he will choose the company of wild whales over people," Phillips said. "I think this is a temporary setback." 

The 26-year-old whale's path to the international limelight began in a dank Mexico City aquarium in 1992 -- when he was cast in the lead role in the Warner Bros. flick Free Willy

The movie, about a troubled boy who helps an aquarium whale return to the wild, was a smash hit -- and led to the revelation of Keiko's deplorable living conditions. 

A massive effort to free Keiko in real life began in 1995. It entailed moving Keiko first to the Oregon Coast Aquarium, where he was prepared for life on his own with lessons in such survival skills as eating live fish. 

In 1998, he was brought to an aquarium in Iceland for more preparation, before being released on Sept. 10, 1998. 

The entire effort cost roughly $20 million, Phillips said. About $15 million of that came from cell-phone magnate Craig McCaw and the McCaw foundation. The rest came from a variety of sources, including donations from children. 

As Keiko continued to swim in the fjord yesterday, no children swam with him. Most of the locals stayed away because of warnings from scientists and local authorities that swimming with Keiko could be dangerous. 

Braden said the Humane Society is talking with officials in Norway -- which still supports commercial whaling -- about keeping curious boaters away from Keiko. 

"It's a big irony that Keiko, the most famous whale in the world, would come to the biggest whaling nation in the world," Phillips said. "He's always creating a challenge."

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