David Letterman delivered a lengthy monologue on his show Thursday explaining the alleged extortion plot against him and admitting that he had sexual relationships with female employees. David Letterman delivered a lengthy monologue on his show Thursday explaining the alleged extortion plot against him and admitting that he had sexual relationships with female employees. (CBS/Associated Press)A producer for CBS News has pleaded not guilty to trying to extort $2 million US from David Letterman over sexual relationships the late-night talk show host had with employees on his show.

Robert (Joe) Halderman entered the plea in Manhattan on Friday, during his arraignment for one charge of attempted grand larceny. The judge set bail at $200,000 US. Halderman posted the bail and was released from custody.

Earlier Friday, Manhattan District Attorney Robert Morgenthau held a news conference and announced that Halderman has been indicted in the alleged blackmail plot. Halderman, a producer on the CBS true-crime show 48 Hours, was arrested on Thursday.

If convicted, Halderman could face a prison sentence of five to 15 years.

Began in September

Morgenthau echoed the account Letterman gave on his show Thursday, saying the famed host discovered a letter and a package of embarrassing emails and photos left for him in September.

It's alleged the letter included threats to reveal information about Letterman's private life, and said it would lead to "a ruined reputation" and damage his professional and family life.

Letterman's attorney took the material to the prosecutor's office and a sting operation by New York police detectives was set up to apprehend a suspect, Morgenthau said.

In a lengthy monologue delivered on his show Thursday, Letterman recounted the extortion plot against him and admitted that he had sexual relationships with female employees who worked on his program, The Late Show. By turns serious and also self-deprecating, the 62-year-old revealed that the plot "has been quite scary."

It was not clear when the relationships took place or how long they lasted. Letterman also said Thursday that he would not comment further on the matter.

Letterman and longtime girlfriend Regina Lasko married in March. They began dating in 1986 and have a son, Harry, born in November 2003.

He was previously a victim of a 2005 plot to kidnap his son and the child's nanny for $5 million US ransom.

With files from The Associated Press