The 69-year-old diplomat was admitted to George Washington University Hospital after falling ill at work on Friday, AP reported.
“This morning, doctors completed surgery to repair a tear in his aorta,” State Department Spokesman Philip J. Crowley said on Saturday.
“He is in critical condition and has been joined by his family,” he added.
Former two-time Assistant Secretary of State and Ambassador to Germany, Holbrooke brokered the 1995 accord that ended the Balkans war. The success brought him one of his seven Nobel Peace Prize nominations.
He has also played a key role in leading American diplomatic efforts in the region in the early days of the Obama Administration.
Holbrooke, who began his long career as a foreign service officer at the American Embassy in Saigon during the Vietnam War, has been alternating between financial executive and diplomat.
Nicknamed “the Bulldozer,” Holbrooke is known for getting warring leaders to the negotiating table, an ability which served him as the US special envoy to Pakistan and Afghanistan.
In 1998, Holbrooke was nominated by former US President Bill Clinton as the American envoy to the United Nations. His appointment, however, was delayed for more than a year as a federal ethics probe was carried out over his second career on Wall Street.
He was also an advisor to Senator John Kerry during his presidential campaign in 2004, as well as Hillary Clinton in the 2008 campaign.