By Michele Walk and Alex Spillius in Washington | 15 Jun 2010
He slumped over his desk a little over an hour into the morning hearing on the current situation in Afghanistan.
It happened just as Sen John McCain saluted him as a "national hero" but questioned if the intended July 2011 withdrawal of troops remained on track.
Military personnel immediately rushed over to the general. After a few moments, the he was revived and was escorted out of the committee room, walking unaided. He returned about 25 minutes later to applause and appeared to be in good spirits.
As he left the Capitol, Gen Petraeus, 57, who was last year treated for early stage prostate cancer, told reporters that he "just got a little lightheaded, a little dehydrated". "It wasn't Senator McCain's question," he added.
He blamed his collapse on not eating breakfast. The hearing has been rescheduled for this morning [weds].
Gen Petraeus had not previously shown any signs of exhaustion or dehydration during the hearing reported that the 30,000-man increase in troop levels would be complete by the August deadline set by President Barack Obama.
In several lengthy appearances before the Senate and House armed services committees in September 2007 to testify on Iraq, Gen Petraeus was reported to have endured great back pain and got through it with the help of pain-relieving drugs.
As the most popular and widely known general of his generation, Petraeus is approaching a new juncture in a career that catapulted him to fame when President George W. Bush sent him to Baghdad in early 2007 to carry out a long-shot "surge" strategy that arguably rescued Iraq from collapse.
Many believe he is the leading candidate to become the next chairman of the Joint Chiefs of Staff, while rumours abound that he is considering a bid for the Republican presidential nomination in 2012 or 2016.
The senators' questioning mostly concerned whether the United States would meet the president's deadline to begin pulling out troops in July 2011.
After insisting throughout the hearing that he supported Mr. Obama's policy, Sen Carl Levin pressed Gen Petraeus for his "best professional judgment" on the withdrawal timeline.
Gen Petraeus hesitated for several moments, and said that even "in a perfect world, we have to be careful with timelines".
He stressed that there was "nuance" to what the president's policy, emphasising that the withdrawal would begin only if certain security, political and development conditions were met. Mr Obama "did not imply a race to the exits," he clarified.
His remarks came as the president promised "disrupt and dismantle" al-Qaeda and to continue reconstruction efforts in Afghanistan to a crowd of National Guardsmen in Florida.