A former Central Intelligence Agency officer was sentenced to 30 months in prison on Friday for blowing a CIA agent's cover, the Justice Department said.

John Kiriakou's sentence as part of a plea agreement marks the first time in 27 years that someone has gone to prison for disclosing a covert CIA agent's name.

Kiriakou was sentenced in federal court in Alexandria, Virginia, a Justice Department spokesman said. He had pleaded guilty in October to one count of disclosing an agent's identity.

His prison term will be followed by three years of supervised release, the spokesman said.

Kiriakou revealed the agent's name in a 2008 email to a reporter. He had repeatedly helped journalists with information on activities such as waterboarding and the CIA's interrogation of al Qaeda operative Abu Zubaydah.

The guilty plea closed one of six prosecutions the Obama administration has pursued against alleged leakers of classified information.

Kiriakou retired from the CIA in 2004. By 2007, he was speaking publicly about waterboarding and his participation in Zubaydah's interrogation.

Defense lawyers for detainees at Guantanamo Bay, Cuba, disclosed in a 2009 military commission filing that they knew the identities of some covert U.S. personnel.

An inquiry led U.S. officials to Kiriakou because the journalist with whom he spoke also talked to a defense team investigator. Prosecutors said the case was unrelated to Kiriakou's 2007 discussion of waterboarding.