Even before its publication, Sidney Sheldon's novel-in-progress, "The Doomsday Conspiracy," is being prepared for a feature film at Warner Bros. Studios.

Producers Joel Silver and Michael Levy, who collaborated on the two "Lethal Weapon" films, have already discussed adaptation of the book with author Sheldon, who said he will be involved in all stages of production of the film.In addition to "The Doomsday Conspiracy," Silver is producing "Hudson Hawk," starring Bruce Willis, on international locations.

- TRI-STAR PICTURES has reached an agreement with writer Dennis Potter to produce a feature film version of his BBC-TV mini-series "The Singing Detective."

Said Tri-Star's Richard Fishoff, senior vice president of the production company, "We're thrilled to be working with Dennis Potter. He has created some of the most strikingly original dramatic material of our generation."

- NICK NOLTE got six days of full-time instruction in speaking like a South Carolina low-country native for his role opposite Barbra Streisand in the upcoming film "Prince of Tides."

Nolte plays a local high school coach in the picture, and speech instructor Wayne Zurenda said he wanted Nolte to avoid sounding like a phony Southerner, as Vivien Leigh did while playing Scarlett O'Hara in "Gone With the Wind."

"That was the most phony accent I've ever heard," Zurenda said.