Marine Staff Sgt. Robert Stufflebeam, on trial for allegedly having had sex with Soviet prostitutes while a guard at the U.S. Embassy in Moscow, pleaded not guilty yesterday to all charges.

Stufflebeam, 25, of Bloomington, Ill., faces as many as 14 1/2 years in prison for illegal contact with Soviet nationals and for lying about it to his superiors.

At the start of the second week of his court-martial at Quantico Marine Corps Base, the defense and prosecution submitted lists of potential witnesses to the military court.

The defense list includes Stufflebeam and Marine Cpl. Arnold Bracy, formerly implicated in the Marines' "sex-for-secrets" scandal at the U.S. Embassy in Moscow. All charges against Bracy were dropped.

The prosecution's list included some of the witnesses who testified in the court-martial of Marine Sgt. Clayton J. Lonetree, convicted last month of spying and sentenced to 30 years in prison.

After Stufflebeam's pleas were entered on three charges, the jury was selected. Stufflebeam was allowed to choose a jury of enlisted personnel, or officers or a combination of those, or have only a judge rule. His case will be heard by five officers and three enlisted personnel.

During interviews of prospective jurors, the defense centered on publicity surrounding the incident and whether the jurors would make a connection between Lonetree and Stufflebeam.

The defense has contended that other Marines, not prosecuted, also were guilty of having contact with Soviet citizens and of not reporting it to superiors.