A Belgian arms dealer has pleaded guilty to illegally exporting airplane engines and parts from the U.S. to Iran for use in aging F-5 fighter jets sold to the Islamic nation before its 1979 revolution.

Jacques Monsieur, along with Iranian national Dara Fotouhi, was charged in a six-count indictment with conspiracy, money laundering and smuggling. Fotouhi, who previously lived in France, remains at large.

Monsieur, who entered the plea Monday, was arrested by federal agents in August when he arrived in New York. Charges were filed in Alabama because the men allegedly wired money to a financial institution in Mobile for the purchase of fighter jet parts.

The maximum penalty is five years in prison and a $250,000 fine, but the plea agreement offers Monsieur, 56, a chance for leniency.

His attorney, Arthur Madden, said the plea agreement speaks for itself but otherwise declined to comment.

"Today's plea underscores the threat posed by Iranian procurement networks and the international arms traffickers who help supply them," said David Kris, assistant attorney general for national security.

According to federal authorities, Monsieur and Fotouhi are experienced arms dealers who have been working with the Iranian government to procure military items and bypass a U.S. arms embargo.

In a news release Monday, the Justice Department said an undercover agent was contacted by Monsieur in February 2009 and they began having regular e-mail contact as well as face-to-face meetings in London and Paris. Monsieur was arrested at JFK International Airport.