DCIA Petraeus Resigns

So reports NBC News, which apparently obtained a copy of Petraeus' statement to the CIA workforce.  From the NBC report's opening:

CIA Director David Petraeus resigned Friday, citing an extramarital affair he had. Multiple sources tell NBC News that Mike Morrell, the deputy CIA director and a longtime CIA officer, would likely be offered the job as acting director but with the understanding that he may be elevated to the job permanently at some point. That's how George Tenet got the job, first as deputy director in July 1995, then acting director following the resignation of John Deutch in December 1996 and finally as director in July 1997, staying on in the Bush Administration.

UPDATE (3:37 p.m.): coverage continues to roll in, from the New York Times, the Washington Post, and Foreign Policy's "the Cable" blog. Like NBC, the latter has a copy of the statement released to CIA personnel, which states in full:

Yesterday afternoon, I went to the White House and asked the President to be allowed, for personal reasons, to resign from my position as D/CIA.  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. This afternoon, the President graciously accepted my resignation. As I depart Langley, I want you to know that it has been the greatest of privileges to have served with you, the officers of our Nation's Silent Service, a work force that is truly exceptional in every regard. Indeed, you did extraordinary work on a host of critical missions during my time as director, and I am deeply grateful to you for that. Teddy Roosevelt once observed that life's greatest gift is the opportunity to work hard at work worth doing. I will always treasure my opportunity to have done that with you and I will always regret the circumstances that brought that work with you to an end. Thank you for your extraordinary service to our country, and best wishes for continued success in the important endeavors that lie ahead for our country and our Agency. With admiration and appreciation, David H. Petraeus

Update #2 (4:10): below is the White House's statement on Petraeus' resignation.

David Petraeus has provided extraordinary service to the United States for decades. 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. As Director of the Central Intelligence Agency, he has continued to serve with characteristic intellectual rigor, dedication, and patriotism. By any measure, through his lifetime of service David Petraeus has made our country safer and stronger. Today, I accepted his resignation as Director of the Central Intelligence Agency. I am completely confident that the CIA will continue to thrive and carry out its essential mission, and I have the utmost confidence in Acting Director Michael Morell and the men and women of the CIA who work every day to keep our nation safe. Going forward, my thoughts and prayers are with Dave and Holly Petraeus, who has done so much to help military families through her own work. I wish them the very best at this difficult time.