Robert (Joe) Halderman, pictured in October, pleaded guilty to attempted grand larceny for trying to extort $2 million US from talk show host David Letterman. (Steve Hirsch/Associated Press)

A TV producer has pleaded guilty to attempted grand larceny for trying to extort $2 million US from David Letterman over the late-night talk-show host's sexual affairs.

Robert (Joe) Halderman entered a guilty plea in a Manhattan court on Tuesday in exchange for six months in jail and community service.

The Manhattan district attorney's office said the debt-strapped Halderman threatened to ruin Letterman's reputation, disguising his demands as a deal for a thinly veiled screenplay about the comedian.

"In September of 2009, I attempted to extort $2 million from David Letterman by threatening to disclose personal and private information about him, whether true or false," Halderman said in a Manhattan court, reading a prepared statement at first so quickly that state Supreme Court Justice Charles Solomon asked him to slow down.

Halderman acknowledged delivering the threat to Letterman's driver, in the form of a screenplay outline or "treatment."

"This so-called treatment was just a thinly veiled threat to ruin Mr. Letterman if he did not pay me a lot of money," said Halderman, who was dressed in a grey suit. He subsequently met with Letterman's lawyer, who eventually gave him a phoney $2-million cheque.

"I knew throughout this time that I was not engaged in a legitimate business transaction with Mr. Letterman and that what I was doing was against New York law," Halderman said, adding that he realized he had violated the privacy of Letterman and his family.

"I feel great remorse for what I have done," Halderman said, apologizing to Letterman, the comic's family and his own former girlfriend, Stephanie Birkett.

He was charged last fall with demanding $2 million to keep quiet about Letterman's love life. The case spurred the comedian to tell Late Show viewers that he had had affairs with women on his staff.

Halderman is a producer for CBS's 48 Hours Mystery.