Sheen, 41, and Mueller, 29, met last year at a party at the home of director Brett Ratner, and Sheen proposed on a recent trip to Costa Rica where he gave Mueller an 11-carat, natural yellow diamond ring, according to Sheen's spokesman, Stan Rosenfield.

The actor has enjoyed a long career in Hollywood that includes work on TV and in movies ranging from 1996 Vietnam war film "Platoon" to baseball comedy Major League.

In Two and a Half Men, Sheen portrays a 40ish bachelor who does not want to grow up and who likes to go out at night and date a lot of women. In many ways, the role mocks Sheen's former real-life image as a Hollywood party boy.

The program finished this past season as the No. 1 comedy on US television, and last year it earned the actor a nomination for an Emmy, the U. TV industry's top honour. It is also aired in many other countries around the world.

Sheen is the son of actor Martin Sheen and brother to actor and director Emilio Estevez. He has been married three times, and has two children with his former wife, actress Denise Richards, from whom he was divorced last year.

Mueller, who is now a Los Angeles real estate agent, had a small role in 2004 film drama A Love Song for Bobby Long.