Two former bellhops charged with selling cocaine to David A. Kennedy shortly before his death last year from a drug overdose decided yesterday not to accept a plea bargain in West Palm Beach, Fla., and asked for a jury trial instead.

Neither prosecutors nor defense lawyers would say why the anticipated arrangement collapsed.

"The decision was made that what we were going to do was not in the best interest of our clients," said Michael Salnick, who represents Peter Marchant, 25, of Warwick, R.I. Salnick said a December trial date is likely.

Marchant and David Dorr, 31, of West Yarmouth, Mass., pleaded not guilty last year to charges of conspiracy and selling cocaine. If convicted, they could be sentenced to 20 years in prison. Dorr had worked as a gardener at the Kennedy summer home in Hyannisport, Mass.

Kennedy, 28, son of the late senator Robert F. Kennedy, was found dead April 25, 1984, on the floor of his room at the Brazilian Court Hotel in Palm Beach, where he had gone to spend the Easter weekend with several members of the Kennedy family at his grandmother's winter mansion.

Kennedy had a long history of drug abuse and had finished a month-long detoxification program in Minneapolis shortly before flying to Palm Beach.

An autopsy after his death found that he had died of an accidental overdose of cocaine; Demerol, a powerful painkiller, and Mellaril, a prescription tranquilizer.