Actor Charlie Sheen Reveals He's HIV Positive

"It's a hard three letters to absorb," the "Two and a Half Men" alum told Matt Lauer.

"I have to put a stop to this onslaught, this barrage of attacks, of sub-truths," the actor said in explaining why he was making the announcement.

Sheen said he was diagnosed with HIV about four years ago. He insisted that it was "impossible" that he could have transmitted the virus to someone else since his diagnosis, while acknowledging that he has had unprotected sex during that time.

The actor said he had been paying off unnamed individuals who had threatened to expose his HIV-positive status. Asked by Lauer if he was still paying those people, Sheen replied, "Not after today, I'm not... I release myself from this prison today."

The NBC morning talk show announced on Monday that Sheen would be making a "revealing personal announcement" on Tuesday's episode.

Sheen's ex-wife, Denise Richards, first learned about his illness a "number of years" ago, Access Hollywood reported Monday. Richards -- and her two daughters with Sheen -- are not infected, as the actor reportedly contracted the virus after the couple's 2006 divorce.

Sheen, 50, had a public meltdown in 2011, which ultimately cost him his starring role on the hit CBS sitcom "Two and a Half Men." He landed on his feet, however, with his FX comedy "Anger Management." Sheen has remained out of the spotlight after FX decided not to renew the show in late 2014 after its 100th episode.

The actor has long struggled with substance abuse and has admitted to soliciting prostitutes in the past, both of which led to several run-ins with the law. He suffered a stroke in 1998 after a cocaine overdose.