NORFOLK, Va. (AP) -- A former sailor pleaded not guilty on Wednesday to additional charges that he passed classified documents to individuals he believed represented the Russian government.

Robert Patrick Hoffman of Virginia Beach was originally charged with attempted espionage in December. But earlier this month, prosecutors filed a superseding indictment that says Hoffman attempted to hand over top secret documents that warned of U.S. capabilities to track foreign ships.

Previously, Hoffman was charged with only passing along secret documents that detailed how to track U.S. submarines. The indictment says Hoffman actually delivered the information to the FBI, which was conducting an undercover operation. The indictment does not allege that the Russian Federation committed any offense under U.S. laws in this case.

The indictment says unauthorized disclosure of secret documents could result in serious damage to national security, while the release of top secret information could result in "exceptionally grave" damage to national security.

The indictment doesn't specify whether Hoffman was going to be paid for the information. But it says he did so with "intent and reason to believe that such information was to be used to the injury of the United States and to the advantage of a foreign nation, namely the Russian Federation."

Hoffman was a cryptologic technician in the Navy who held top secret clearance and retired in November 2011.

Hoffman, originally from Buffalo, N.Y., served in the Navy for 20 years, and retired with the rank of petty officer first class. In 1992, 2001 and 2009, Hoffman signed classified information non-disclosure agreements with the U.S. government, according to the indictment

A jury trial is scheduled for June 17, although defense attorneys have asked for that date to be pushed back. If convicted, Hoffman could face up to life in prison.