As expected, Lance Armstrong admitted to Oprah Winfrey Monday that he used performance-enhancing drugs to keep a leg up on the competition during his cycling career.

The details of the interview were supposed to remain a secret until it airs on Thursday at 9 p.m. ET on the Oprah Winfrey Network, but an anonymous source confirmed Armstrong's apology to USA Today. Oprah herself didn't confirm what Armstrong said, but took to Twitter to reveal the interview lasted more than two-and-half hours and that Armstrong "came ready!" She'll appear on CBS This Morning to promote the interview.

Prior to sitting down with Oprah, Armstrong gave a "very sincere and heartfelt apology" to the staff of about 100 at his Livestrong charity's headquarters in Austin, Texas, a spokesman said.