SAN DIEGO (AP) _ The onetime chief of staff to former Gov. Jerry Brown has been sentenced to 46 months in prison for conspiring to launder $300,000 that an undercover FBI agent told him was Colombian drug money.

U.S. District Judge J. Lawrence Irving on Monday also fined Richard Silberman $5,500 and said he would decide by next week whether to raise that to the maximum $75,000.

Silberman was arrested at a San Diego hotel in April 1989. Prosecutors said he was attempting to negotiate a $1.1 million money laundering deal with FBI agent Peter Ahearn, whom Silberman thought was an associate of Colombian cocaine traffickers.

Silberman apologized before his sentencing ''for the hurt and the pain'' he caused his wife, San Diego County Supervisor Susan Golding, and other family members.

''I accept full responsibility for what I did and it won't happen again,'' he told Irving.

Silberman, 61, was Brown's chief of staff in the 1970s and an influential Democratic party fund-raiser for years. The former financier also served on several state commissions and donated money to many non-profit groups in San Diego.

''It is clear to me that you have achieved more than most men could ever dream of. Your contributions to this community have been significant,'' Irving told him during sentencing.

''What boggles my mind is that you chose to become ... part of the chain that brought poison into the community that you had supported for years.''

Silberman was accused of masterminding the laundering of $300,000 in purported drug profits during the FBI scam.

A jury convicted him in June of structuring a financial transaction to avoid federal currency laws, but deadlocked on six other counts, including conspiracy.

He pleaded guilty Aug. 24 to the single conspiracy count in exchange for the dropping of the other charges.

Authorities say Chris Petti, a reputed mobster, introduced Silberman to Ahearn through Robert Benjamin, a longtime acquaintance of Petti's who was working secretly as a government informant. Petti faces trial Oct. 3.

In his plea bargain, Silberman admitted exchanging $100,000 for shares of Yuba American Gold Ltd. stock for Ahearn in November 1988. The company was a financially strapped Northern California gold-mining venture Silberman headed at the time.

Ahearn and Silberman conducted a $200,000 transaction three months later. Silberman testified during his trial that it was the agent's idea to buy U.S. Treasury bonds that time instead of more Yuba American Gold stock.

He also testified he didn't want to complete the second deal, but Benjamin threatened to harm him and his family if he didn't.

Golding appeared dejected as she sat behind her husband with her teen-age daughter and other family members at Monday's sentencing.

''I love you,'' she called out as he was led off to jail.

''The only thing I can say is that when someone you love is in trouble, you do the best to stand by them,'' she said outside court.