Mark Chavez, 54, of San Diego, stood in court with his lawyer  on Friday and told a judge he understood his rights.

United States Magistrate Judge Jean Rosenbluth told him he could remain free on bond with several restrictions, including turning over his passport and not working as a doctor. He has agreed to turn over his medical license.

Chavez signed an agreement with prosecutors earlier this month to plead guilty to conspiring to distribute the surgical anaesthetic ketamine.

He did not enter his guilty plea or speak about the case, which he will do with another judge at a date to be determined.

"He's incredibly remorseful," Chavez's lawyer Matthew Binninger said outside court with the doctor standing at his side.

"He's trying to do everything in his power to right the wrong that happened here. He didn't accept responsibility today but only because it wasn't on the calendar."

Binninger added, "He's doing everything in his power to cooperate and help with this situation."

The lawyer said Perry was "universally beloved, and it's a shame what happened."

Chavez would be the third person to plead guilty in the aftermath of the Friends star's fatal overdose last year.

He also agreed to cooperate with prosecutors as they pursue others, including the doctor Chavez worked with to sell ketamine to Perry.

Also working with the US Attorney's Office are Perry's assistant, who admitted to helping him obtain and inject ketamine, and a Perry acquaintance, who admitted to acting as a drug messenger and middleman.

The three are helping prosecutors as they go after their main targets, doctor Salvador Plasencia, charged with illegally selling ketamine to Perry in the month before his death, and Jasveen Sangha, a woman who authorities say is a dealer who sold the actor the lethal dose of ketamine.

Both have pleaded not guilty and are awaiting trial.

With AAP.