Washington (CNN) -- U.S. diplomat Richard Holbrooke was in critical condition at George Washington University Hospital on Saturday after undergoing surgery to repair a tear in his aorta, a State Department spokesman said.
Holbrooke, 69, the Obama administration's special representative for Pakistan and Afghanistan, fell ill Friday morning during a meeting with Secretary of State Hillary Clinton and walked down to the department's medical unit, a senior State Department official said. He was taken by ambulance to the hospital, the official said.
CNN's Chief Medical Correspondent Sanjay Gupta said the tearing of one of the layers of the walls of the aorta "happens suddenly." It typically is associated with blood pressure and typically occurs in men between the ages of 50 and 70.
Gupta said the biggest concern that blood leaving the heart and heading "to other places in the body may not be doing that as well." The location of the tear "would determine what, if any, other side effects would occur."
"This is different from a problem people think of with the heart where some of the blood vessels going to the heart become blocked," he said.
An operation "typically involves bringing layers of the aorta back together so that no further dissection can occur. If that's done quickly and the aorta is intact, meaning it hasn't opened up, that can be a very good procedure and can take care of the problem."
After doctors completed surgery on his aorta Saturday morning, Holbrooke was joined by his family, State Department spokesman P.J. Crowley said.
President Barack Obama called the diplomat's wife, Kati, and told her he and first lady Michelle Obama have Holbrooke in their prayers, the White House said in a statement.
"Richard Holbrooke is a towering figure in American foreign policy, a critical member of my Afghanistan and Pakistan team, and a tireless public servant who has won the admiration of the American people and people around the world," the president said.
Secretary Clinton visited Holbrooke at the hospital on Saturday, the State Department said.
Holbrooke is a career diplomat best known for brokering the peace agreement between Bosnian factions in 1995 that became the Dayton accords.
CNN's Elise Labott contributed to this report.