SAN FRANCISCO — Barry Bonds' trainer Greg Anderson told a judge Friday he won't testify at the slugger's perjury trial, while federal prosecutors mulled whether to appeal a key ruling and delay the start of the case.

U.S. District Court Judge Susan Illston said the trial would likely be postponed if the government files an appeal.

Illston told Anderson at a hearing that she will order him to testify on Wednesday when attorneys are slated to deliver their opening statements to the jury. Anderson said that he will disobey the order.

The judge said Anderson will be incarcerated during the trial for contempt of court until he changes his mind or for the length of the proceedings, which are expected to last a month. He was previously imprisoned for refusing to testify about Bonds before a grand jury.

Whether the trial would start on schedule Monday was still unclear.

Illston has barred prosecutors from showing jurors three positive steroid tests they allege belong to Bonds, as well as so-called doping calendars investigators say that Anderson maintained for baseball's career home run leader.

The judge said an appeal of her ruling would almost certainly delay the trial. The judge said her reading of the law requires her to automatically stop proceedings to allow the 9th U.S. Circuit Court of Appeals to consider the government's appeal.