Retired Marine Gen. James E. Cartwright pleaded guilty to a single count of making false statements to federal authorities. The investigators were looking into a leak of classified information about a secret cyberattack on Iran's nuclear facilities.
The plea came in a brief appearance in U.S. District Court in Washington, D.C.
According to the Associated Press, Cartwright could face a maximum of five years in prison but prosecutors and defense counsel have agreed on a recommended sentence of no more than six months. U.S. District Judge Richard Leon will announce his decision at a sentencing hearing scheduled for January 2017.
Cartwright is a former vice chairman of the Joint Chiefs of Staff. He had been charged with falsely telling FBI investigators that he did not provide classified information for a book written by New York Times reporter David Sanger.
Sanger is author of Confront and Conceal: Obama's Secret Wars and Surprising Use of American Power, published in 2012. It covers the administration's use of a computer virus known as Stuxnet to temporarily knock out Iran's ability to enrich uranium in 2010.
As the Washington Post reports, the U.S. and its ally, Israel, have never confirmed suspicions that they were responsible for that cyberattack.
The indictment released on Monday also charged Cartwright with misleading investigators about classified information shared with another journalist, Daniel Klaidman. The document does not identify the Sanger book or the country Cartwright and Klaidman discussed in an email.
In a written statement issued after the hearing, Cartwright said, "It was wrong for me to mislead the FBI on November 2, 2012, and I accept full responsibility for this. I knew I was not the source of the story and I didn't want to be blamed for the leak. My only goal in talking to the reporters was to protect American interests and lives; I love my country and continue to this day to do everything I can to protect it."
The lead prosecutor, Rod Rosenstein, did not make a public statement outside the courthouse.
The guilty plea is a steep fall for a general who had ranked among the top U.S. military leaders. According to the New York Times, Cartwright, a former Marine Corps fighter pilot, was known as President Obama's favorite general and once considered a leading candidate for chairman of the Joint Chiefs of Staff.
After the publication of Sanger's book, congressional Republicans demanded a criminal investigation of the leak of classified information. Cartwright was not charged with being the source of the leak itself, but with lying in the course of the investigation.