By Ros Krasny

BOSTON (Reuters) - A Massachusetts man charged with plotting to attack the Pentagon and the U.S. Capitol with large, remote-controlled model airplanes packed with explosives has agreed to plead guilty, authorities said on Tuesday.

Prosecutors and defense attorneys have agreed to request a 17-year sentence for Rezwan Ferdaus on charges that he attempted to damage and destroy a federal building, and attempted to provide material support to terrorists.

Ferdaus, 26, of Ashland, Massachusetts, earlier pleaded not guilty to a total of six charges after his arrest in September 2011 after an undercover FBI investigation.

In exchange for the guilty plea, the government will dismiss the remaining charges.

A U.S. citizen and a physics graduate from Northeastern University, Ferdaus was arrested after an FBI investigation during which he requested and took delivery of explosives, three grenades and six assault rifles from undercover FBI agents.

At the time of his arrest, Ferdaus had obtained one remote-controlled aircraft, a scale model of a U.S. Navy F-86 Sabre fighter jet about the size of a picnic table, which he kept in a storage locker rented under a false name.

Authorities said the public was never in danger from the explosives and weapons, which they said were always under the control of federal officials during the sting operation.

The government had previously alleged that Ferdaus told undercover agents of his plans to commit acts of violence against the United States by decapitating its "military center" and killing "kafirs," an Arabic term meaning non-believers.

In 2010, already under surveillance, Ferdaus allegedly supplied 12 mobile phones rigged as electrical switches for improvised explosive devices to FBI agents whom he believed to be members of or recruiters for al Qaeda.

Ferdaus' attorneys suggested during a bail hearing in November that their client had mental health issues, and that his attack plan was "fantasy."

(Reporting By Ros Krasny; Editing by Doina Chiacu)