SAN FRANCISCO — Barry Bonds' trainer Greg Anderson has told a judge he will refuse to testify at the slugger's perjury trial.

Anderson said he will keep silent today at a hearing ordered by U.S. District Court Judge Susan Illston, who wanted to determine Anderson's intentions without a jury present. Bonds' trial is scheduled to begin Monday.

Without Anderson's testimony, the judge is barring prosecutors from showing jurors key evidence such as positive drug tests alleged to have belonged to Bonds.

Prosecutors said in court papers they will demand Anderson be jailed for contempt. Anderson previously served a year in prison for refusing to testify before a grand jury.

Bonds is accused of lying to a grand jury when he denied he knowingly took performance-enhancing drugs.