David Petraeus stepped down as the director of the CIA on Friday, citing an affair.
"After being married for over 37 years, I showed extremely poor judgment by engaging in an extramarital affair. Such behavior is unacceptable, both as a husband and as the leader of an organization such as ours," he said in a letter sent to colleagues.
A retired U.S. Army general who served as the top U.S. commander in Iraq and Afghanistan, Petraeus, 60, was sworn in as the head of the CIA in September 2011.
President Barack Obama accepted his resignation during a phone call Friday, according to a senior administration official.
The two men met Thursday. During that meeting, Petraeus offered his resignation to the president and explained the circumstances behind it, the official said.
"By any measure, he was one of the outstanding general officers of his generation, helping our military adapt to new challenges, and leading our men and women in uniform through a remarkable period of service in Iraq and Afghanistan, where he helped our nation put those wars on a path to a responsible end," Obama said about Petraeus.
"As director of the Central Intelligence Agency, he has continued to serve with characteristic intellectual rigor, dedication and patriotism."
The president expressed confidence the CIA will move forward under the direction of Acting Director Michael Morell.
Morrell, a career agency officer, was sworn in as deputy director of the CIA in May 2010.
Director of National Intelligence James Clapper issued a statement Friday confirming that Petraeus had turned in his resignation, saying his "decision to step down represents the loss of one of our nation's most respected public servants."
Rep. Peter King, chairman of the House Committee on Homeland Security, praised Petraeus as a "true American patriot."
Petraeus and his wife, Holly, live in Virginia. They have two grown children, a son and a daughter.
CNN's Suzanne Kelly and Jill Dougherty contributed to this report.
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