NEW YORK (Reuters) – A man charged last year in a suspected Iranian-backed plot to kill the Saudi ambassador to Washington was expected to plead guilty on Wednesday to terrorism-related charges, a person familiar with the matter said.

U.S. authorities accused Manssor Arbabsiar, 57, in October 2011 of being tapped by Iran’s security agencies to assassinate Saudi Ambassador Adel al-Jubeir.

Arbabsiar, who was arrested on September 29, 2011, when he arrived at John F. Kennedy International Airport from Mexico, is a naturalized U.S. citizen and holds an Iranian passport.

He previously pleaded not guilty in federal court to charges including conspiracy to commit an act of terrorism and conspiracy to murder a foreign official.

A plea hearing was scheduled on Wednesday before U.S. District Judge John Keenan, said the source, who asked not to be identified because the plea had not taken place.

Arbabsiar’s court-appointed attorney, Sabrina Shroff, did not immediately return a call seeking comment.

According to the court documents, the plot began to unfold in May 2011 when Arbabsiar approached an individual in Mexico, who was posing as an associate of an unidentified drug cartel. That individual was actually a paid informant for the U.S. Drug Enforcement Administration.

The unidentified individual immediately tipped law enforcement agents about the plot, according to the criminal complaint. Arbabsiar paid $100,000 to the informant in July and August, a down payment on the $1.5 million requested by the source to carry out the plot, according to the complaint.

Authorities said no explosives were acquired for the plot.

Arbabsiar had faced up to a life term in prison on the original charges.