A lawyer says an Iranian graduate student studying at the University of Texas has gone on trial in Tehran on charges of having "relations with a hostile country" and receiving "illegitimate funds."

Saeed Khalili says his client, Omid Kokabee, pleaded not guilty to both charges at the opening session of his trial Tuesday, October 4.

Iranian authorities arrested the 29-year-old Kokabee in February at the Tehran airport. He was studying optics in the physics department at the University of Texas.

Khalili said that he has not been able to speak with Kokabee yet, The Associated Press reported.

Though Iran and the United States have no diplomatic relations, many Iranian students apply to study in the U.S. every year.