NEW YORK (Reuters) - Lance Armstrong "did not come clean in the way I expected" on whether he used performance-enhancing drugs in his cycling career, celebrated talk show host Oprah Winfrey said on Tuesday, a day after a lengthy interview with the disgraced athlete.

Armstrong, 41, has always vehemently denied using the drugs and had never tested positive to a doping test. But the evidence against him has been overwhelming and pressure has been building on him to admit that he cheated.

USA Today reported on Monday that Armstrong had confessed to the doping in the interview with Winfrey, which will air on Thursday and Friday on Winfrey's OWN Network, and other media say they have confirmed the report.

In an appearance on CBS' "This Morning" show on Tuesday, Winfrey stopped short of confirming a confession and said she would leave to others to decide if Armstrong had been contrite in the interview. She added that she found him to be thoughtful and serious.

When asked why Armstrong, who had his seven Tour de France titles stripped last year, had agreed to an interview that lasted more than two hours, Winfrey said: "I think he was just ready."

"I didn't get all the questions asked, but I think the most important questions and the answers that people around the world have been waiting to hear were answered," Winfrey told CBS.

A cancer survivor who went on to become the greatest cyclist the world has seen, Armstrong's fall from grace has been as swift and spectacular as his rise through the French Alps.

Long dogged by accusations he cheated his way to the top, an October report from the U.S. anti-doping body USADA ultimately triggered his rapid slide.

USADA exposed Armstrong as a liar and a cheat, describing him as the ringmaster of the "most sophisticated, professionalized and successful doping program that sport has ever seen," involving anabolic steroids, human growth hormone, blood transfusions and other doping.

(Reporting by Dan Burns; Editing by Paul Simao)