Former presidential aide Oliver L. North is trying to prevent prosecutors in his Iran-Contra criminal trial from attending closed hearings that begin this week on classified documents in the case.

A brief court filing Monday by lawyers for the former National Security Council aide did not list any reasons for barring the prosecutors. But the defense presumably is prepared to argue that allowing prosecutors to attend would give them an unfair look at North's trial strategy.North is charged with conspiring to divert millions of dollars in profits from the Reagan administration's secret weapons deals with Iran to the Nicaraguan Contra rebels.

This week's hearings were scheduled by U.S. District Judge Gerhard A. Gesell to hear defense objections to deletion of sensitive material from classified documents that special prosecutor Lawrence Walsh wants to use as evidence.

Gesell has directed North to come to the hearing prepared to say why the material is relevant to his defense and should not be deleted.