NEW YORK • Troubled television star Charlie Sheen may have freed himself from blackmail by publicly disclosing on Tuesday that he is HIV-positive, but he might have opened the door to other legal problems.

During a live interview with Matt Lauer on NBC's Today show, Sheen, 50, said he had paid people upwards of US$10 million (S$14.3 million) to keep quiet about his condition and that part of his goal in coming forward was to put an end to the payments.

HIV refers to human immunodeficiency virus and causes Aids, or acquired immune deficiency syndrome.

He asserted that it was "impossible" he had knowingly transmitted the disease to other people.

He said he had unprotected sex with two people, but that both people were informed and have been under the care of his doctor.

He said he had disclosed his diagnosis, which he had known for about four years, to all of his sex partners.

Hours after the interview, one of his former girlfriends said she learnt about his HIV diagnosis "right along with everyone else".

Bree Olson, a former actress in pornographic movies, said she was involved with Sheen for about a year and lived with him for about six months during the time after his HIV diagnosis.

"He never said anything to me," she said on Howard Stern's SiriusXM Radio show. "I was his girlfriend. I lived with him. We were together. We had sex almost every day for a year - with lambskin condoms."

She said she has tested negative for HIV and has not thought about taking any legal action against him.

Sheen's manager Mark Burg told People magazine the actor was not infected at the time of the relationship.

Sheen was "100 per cent HIV- negative" when he lived with Olson in early 2011 and he was given the diagnosis after he fired her from his My Violent Torpedo Of Truth/ Defeat Is Not An Option live performance tour, Mr Burg said.

Under California's criminal statute, a person who knowingly exposes another to HIV through unprotected sex must be proved to have had a deliberate intent to infect them.

The Los Angeles police and county prosecutors said they were not aware of any criminal cases regarding Sheen's sexual activity while HIV-positive.

However, law professor Scott Burris at Temple University said there was "no question that (Sheen) could face a number of civil lawsuits and he could lose any one of those suits".

In 2011, Sheen had a drug-fuelled public meltdown and was fired from his hit CBS sitcom, Two And A Half Men.

By his own timeline given on Tuesday, 2011 would be about the time he learnt of his diagnosis.

In the interview with Today, he was not asked about any link between the diagnosis and the breakdown.

But in an open letter released on the show's website after the interview, he said he started treatment, but fell into a downward spiral out of anger, shame and disbelief.

He called it "a temporary yet abysmal descent into profound substance abuse and fathomless drinking" and "a suicide run".

On Today, his doctor Robert Huizenga said the treatment had suppressed the virus and that the actor did not have Aids and was "absolutely healthy".

Sheen said he is not taking recreational drugs anymore, but does drink "a little bit".

REUTERS, NEW YORK TIMES, AGENCE FRANCE-PRESSE