NEW YORK (Reuters) - Notre Dame football star Manti Te'o told ABC News' Katie Couric that he had lied to keep up a hoax involving a nonexistent dying girlfriend once he learned he had been duped two days before the Heisman Trophy winner was announced.

In a preview of the interview shown on Wednesday on "Good Morning America," Te'o talked about the girlfriend, Lennay Kekua. He mourned her September 12 death from cancer, but it later turned out that she never existed except as part of an online fraud.

On December 6, two days before the prestigious college football trophy was awarded, Te'o said he had received a phone call from a woman claiming she was Kekua.

"Now I get a phone call on December 6, saying that she's alive, and then I'm going be put on national TV two days later," Te'o told Couric. "And to ask me about the same question. You know, what would you do?"

A Heisman contender, Te'o was passed over for the award, which went to Texas A&M quarterback Johnny Manziel.

"You stuck to the script," Couric said. "And you knew that something was amiss, Manti."

Te'o replied: "Katie, put yourself in my situation. I, my whole world told me that she died on September 12. Everybody knew that. This girl, who I committed myself to, died on September 12."

The interview will be broadcast in its entirety on the daytime talk show "Katie" on Thursday.

This is Te'o's first on-camera interview since news broke of the fraud behind one the most widely recounted U.S. sports stories last year as Notre Dame made a drive toward the college football national championship game.

Couric interviewed Te'o, who in an interview with ESPN last week denied being in on the elaborate hoax, and his parents, Brian and Ottilia Te'o.

"Now many people writing about this are calling your son a liar," Couric said. "They are saying he manipulated the truth, really for personal gain."

Brian Te'o dismissed such statements. "People can speculate about what they think he is," he said. "I've known him 21 years of his life. And he's not a liar. He's a kid."

Notre Dame, one of the most powerful institutions in U.S. collegiate athletics, held a news conference within hours of the Deadspin.com article that exposed the hoax to say that Te'o had been duped.

(Writing by Barbara Goldberg; Editing by Lisa Von Ahn)