Special Representative for Afghanistan and Pakistan Richard Holbrooke fell ill today during a meeting in Secretary of State Hillary Clinton's office, officials said.
According to Democratic sources, Ambassador Holbrooke, Secretary Clinton's top aide for the region, gasped and was clearly undergoing a medical situation when he became ill. He is said to have walked out of her office on his own power and was tended to by medical personnel at the State Department before being transported to George Washington University Hospital where to be treated for a blood clot.
State Department spokesman P.J. Crowley refused to confirm Ambassador Holbrooke's condition, but confirmed that he is in the hospital.
"All I can tell you is that the ambassador is at the hospital at the present time," Crowley told reporters. "He was here working this morning [and] he was taken to the hospital for evaluation."
Several officials, who spoke on the condition of anonymity, told ABC News that Holbrooke was undergoing tests and one official said he was doing "ok."
Ambassador Holbrooke was named to his current post just days after President Obama took office in January 2009 and was immediately tasked with overhauling the United States' efforts in Afghanistan and Pakistan. He is known best for his bombastic personality and stamina, having traveled to the region numerous times since taking office.
The veteran diplomat is a former two-time Assistant Secretary of State, Ambassador to Germany, and was a key player in the Dayton Peace accords, which brokered an end to the conflict in Bosnia. He began his long career as a foreign service officer at the U.S. embassy in Saigon during the Vietnam War.
ABC News' Jake Tapper contributed to this report.