Hollywood star Charlie Sheen has confirmed he is living with HIV in a US television interview.
"I am here to admit that I am HIV positive," he said.
The former star of sitcom Two And A Half Men appeared on NBC's Today show, ending days of intense media speculation.
Sheen revealed to Matt Lauer he had paid "enough to take it into the millions" to keep people from going public about his illness.
"I have to put a stop to this onslaught, this barrage of attacks and of sub-truths," he said, adding he was diagnosed four years ago.
He said when he revealed his HIV status to friends "the truth became treason", leading to "blackmail and extortion and a circle of deceit".
"I trusted them, they were in my inner circle and thought they could be helpful. My trust turned to their treason," he said, adding a prostitute took a picture of his medication and threatened to sell it to newspapers.
"I think I release myself from this prison today," he said.
He admitted that his use of drink and drugs was a "bad decision" but said it was "impossible" that he would have passed HIV on to anyone else.
The actor said he does not know how he contracted the virus but stressed he does not feel any stigma attached to the illness.
Speaking about the time prior to his diagnosis, he said: "It started with a series of cluster headaches and sweating - I was hospitalised. I thought I had a brain tumour - after tests they said this was the situation. It's a hard three letters to absorb."
Sheen appeared with his doctor, Robert Huizenga, who said his daily medication has suppressed the virus and he is "absolutely healthy".
"Charlie has an undetectable level of the virus in his blood," he said.
When asked to respond to rumours Sheen has Aids, Dr Huizenga said: "Charlie does not have Aids - that's when the virus suppresses the immune system. He is healthy."
'Shame and anger'
Sheen said he is taking prescribed drugs daily and despite his erratic tendencies, has never missed a day's medication.
He said he is no longer taking recreational drugs but admitted he still "drinks a bit".
Dr Huizenga said he did have concerns Sheen might omit to take his medication.
"We're petrified about him, we're so, so anxious that if he was overly depressed or abusing substances he'd forget to take a pill, but he's managed to take his medication," he said.
When asked if he would stop drinking, Sheen responded by saying: "Perhaps the freedom of today might lead to that as well."
Sheen said his "personal disbelief and shame and anger" at the initial diagnosis "led to a descent into substance abuse and fathomless drinking".
But now he feels he has "the responsibility to better myself and help a lot of other people. With what we're doing today, others may come up and say, 'Thanks Charlie, thanks for kicking the door open'."
He said he hoped the media pressure would ease now.
"You can never predict how the media will roll with something," he said. "I hope it's a lot more forgiving and supportive than a lot of the garbage I've read over the past few days - that I knew I had Aids and was intentionally spreading it.
"It's as far from the truth as can be."
HIV facts by Michelle Roberts, Health editor, BBC website
There are many different ways that you might catch HIV, but the main ones are having unprotected sex or sharing needles or syringes.
HIV is transmitted via blood, not saliva, but it is possible to catch HIV through unprotected oral sex (although the risk is much lower than with vaginal or anal sex).
Once infected, the virus attacks the person's immune system, making them more prone to other infections and diseases.
There is no cure for HIV, but there are treatments that mean people with the virus can live a long and healthy life.
The best way to prevent HIV is to use a condom for sex and to never share needles or other injecting equipment.
The actor rose to fame in the 80s with hit films including Platoon and Wall Street and, in 2011, was the highest-paid actor on TV thanks to his sitcom role.
But he has frequently struggled with drink and drug abuse.
The star, who played a hedonistic bachelor in Two And A Half Men, was fired from the show in 2011 after a downward spiral in his personal life, often played out in public.
Production had been suspended after he entered rehabilitation for reported drug and alcohol abuse.
The actor - the youngest son of West Wing star Martin Sheen and brother of actor Emilio Estevez - has also had a colourful personal life and has been married three times.
Sheen's first daughter, Cassandra was born to his former high school girlfriend.
His first marriage, to Donna Peele, ended after a year. His second marriage was to former Bond girl Denise Richards, with whom he has two daughters. They divorced in 2006 and he married Brooke Mueller, with whom he has twin sons.
He was then due to marry adult film star Scottine Ross, but the wedding was called off.
The actor said he had told Richards and Mueller and his oldest daughter about his diagnosis.