Charlie Sheen confirmed Tuesday on the Today Show that he is HIV positive, having been diagnosed "roughly four years ago."

"It's a hard three letters to absorb," the actor said. "It's a turning point in one's life."

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In an honest and blunt interview, Sheen told host Matt Lauer he finally had to speak about his condition in order to "put a stop to this barrage of attacks of sub-truths and very harmful and mercurial stories that threaten the health of so many others."

The Golden Globe-winner also revealed he faced years of blackmail, giving millions of dollars in extortion money to prostitutes with whom he had relations in hopes that they would keep his HIV status a secret.

"My trust turned to their treason," he said.

But when Lauer asked Sheen why he would continue this behavior despite the extortion and his health, the actor admitted that he was driven by depression and drug and alcohol abuse.

"That part I own," Sheen said, adding that it's "impossible" he has transmitted the disease to others — though he did also admit having unprotected sex with two individuals, whom he says were warned beforehand and "under the care" of his doctor.

Sheen's doctor, Robert Huizenga, also appeared on Today to discuss the actor's health, saying Sheen has an "undetectable level of the virus in his blood" and clarifying that he does not have AIDS, despite rumors circulating in the media.

Lauer expressed concern over Sheen's lifestyle, wondering if HIV had finally put an end to his notorious drug and alcohol use. Sheen said he had stopped using drugs, but still drinks — behavior he doesn't believe will ever, or has ever, deter him from taking his medication.

But the actor remained positive throughout the interview, saying while he doesn't want to be the "poster man" for the condition, he will represent it as he sees fit.

"If there was one guy on this planet to contract this that’s going to deliver a cure," he said, with typical Sheen bravado, "it’s me.”

Sheen also penned an open letter, published on Today.com Tuesday, which detailed his diagnosis and the subsequent reaction which led him into "profound substance abuse and fathomless drinking."

It was a suicide run. Problem was, I'd forgotten that I'm too tough for such a cowardly departure. Yet, despite this loathsome and horrific odyssey, I was vigilant with my anti-viral program.. ..My partying days are behind me. My philanthropic days are ahead of me.

In the United States, more than 1.2 million people have HIV, and about 50,000 people are newly infected each year, Today reports.

The 50-year-old former Two and a Half Men and Anger Management star has been married three times — to Brooke Mueller (2008–2011), Denise Richards (2002–2006) and Donna Peelefive (1995–1996) — and has five children. Sheen was the highest-paid actor on TV in 2010.