Notre Dame star linebacker Manti Te'o acknowledged to ABC's Katie Couric that he maintained the illusion of his dead girlfriend in the weeks after he received a call claiming that Lennay Kekua and her death were hoaxes.

His publicist, Matthew Hiltzik, who also reportedly represents Couric, said he was present during the interview. He insists his client was not lying. Rather, he was trying to determine the truth after learning a woman he thought was his girlfriend had not died and may never have existed. Hiltzik takes issue with Te'o being called a liar, he said.

"Lance Armstrong is a liar. Manti Te'o made one big mistake: not telling his father the truth," he said, referring to a statement his father made last year, claiming Te'o and Kekua had met in person.

During the interview, set to air on Couric's syndicated show Thursday, the Heisman Trophy runner-up said he mentioned Kekua and her death to reporters after receiving a December 6 phone call from someone he thought was Kekua, saying she was not dead.

"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," Te'o said, according to clips released on the ABC News website.

Te'o has said he believed Kekua, whom he thought was his girlfriend despite never meeting her face to face, had died of leukemia on September 12 after a car accident left her hospitalized.

"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. And to ask me about the same question. You know, what would you do?" Te'o said, according to clips of the interview.

Hiltzik asserted Thursday that it would be have been "crazy and stupid and short-sighted" for Te'o, who was still trying to determine what had happened, to tell reporters that his girlfriend -- the story of whose death helped propel him into the national spotlight -- may have been an elaborate concoction.

On December 8, ahead of the Heisman Trophy presentation, Te'o said he "lost both my grandparents and my girlfriend to cancer." In a New York Post interview published more than three weeks later, Te'o said memories of his grandfather helped him cope with the losses of his grandmother and girlfriend, whom he'd previously said died on the same day.

"So when I lost my grandmother and Lennay, I thought of him. He was my strength," Te'o told the Post, according to a December 30 article.

It was true that his grandmother had died, but Te'o conceded that he mentioned Kekua again even after -- as Couric put it -- he "knew that something was amiss," according to the interview clips.

While he said he didn't know whether the now-debunked storyline helped him place second in Heisman Trophy voting, he insisted his emotions surrounding Kekua's loss were authentic.

"What I went through was real. You know, the feelings, the pain, the sorrow -- that was all real, and that's something that I can't fake," he said.

Couric said she believes Te'o sincerely thought he was having a relationship with Kekua. Couric said she heard voice mail messages on Te'o's phone, allegedly from Kekua, and even saw his phone bill.

"There were multiple calls to this number, where he would stay on the phone for hours," Couric told ABC's "World News with Diane Sawyer" on Wednesday.

Te'o denied reveling in the attention he received for playing so outstandingly on the gridiron after suffering such devastating personal losses.

"I think, for me, the only thing that I basked in was that I had an impact on people; that people turned to me for inspiration. And I think that was the only thing I focused on," the Hawaii-born Mormon said. "My story, I felt, was a guy who in times of hardship and in times of trial, held strong to his faith, held strong to his family, and I felt that was my story."

Te'o's parents, Brian and Ottilia Te'o, were on hand for the interview. Couric said she believes they were as stunned as their son when they found out Kekua didn't exist. Te'o's mother talked to the woman many times on the phone, and his father texted biblical passages to the woman and discussed them with her, Couric said.

Te'o's father was quoted in an October article in the South Bend Tribune, saying his son and Kekua had met at a football game in Palo Alto, California, and exchanged numbers. Their love affair ensued from there, the paper reported.

Last week, Te'o said, however, that he had lied to his dad because he was embarrassed to admit he was in love with a woman he'd never laid eyes on.

"I knew that -- I even knew that it was crazy that I was with somebody that I didn't meet," he told ESPN. "And that alone, people find out that this girl who died I was so invested in, and I didn't meet her as well."

Asked his response to those who say his son is a liar who "manipulated the truth, really for personal gain," Te'o's father gave a tearful reply, according to ABC.

"People can speculate about what they think he is. I've known him 21 years of his life, and he's not a liar. He's a kid," Te'o's father told Couric.

Questions have also been raised about Te'o telling Sports Illustrated in October that Kekua had attended one of his games, when he issued a statement last week saying he'd never met her.

Because ABC News has made public only snippets of the interview, it's not clear which parts of the hoax Te'o will address, but the Notre Dame standout has said he's sure he'll be vindicated.