Richard Holbrooke, the US special envoy for Afghanistan and Pakistan, remained in critical condition after undergoing an additional surgery on Monday to repair a torn aorta.
Mr Holbrooke, 69, was admitted to the intensive care unit of the George Washington hospital here on Friday after he fell ill at the Foggy Bottom headquarters of the state department.
Obama's point man for Afghanistan and Pakistan, Mr Holbrooke underwent a surgery on Saturday to repair a tear in his aorta, the large artery that takes blood from the heart. He underwent an additional surgery on Monday.
"On Monday, Ambassador Mr Holbrooke underwent an additional procedure to improve circulation following on Sunday’s surgery," the state department spokesman P J Crowley said, adding that Mr Holbrooke remains in critical condition, and is surrounded by his family, friends, colleagues and staff.
Mr Holbrooke's family continued to receive calls from a number of world leaders including the Afghanistan President, Hamid Karzai, and the Pakistani President, Asif Ali Zardari.
"On Monday Ambassador Mr Holbrooke's wife, Kati Marton, received calls from President Mr Karzai and President Mr Zardari; secretary Clinton also spoke with President Mr Karzai," Crowley said.
"His family is grateful for the outpouring of support and prayers coming in from his many friends, colleagues and leaders around the world," he said.
US President Barack Obama on Saturday said he is a "towering personality" of American diplomacy.
"Mr 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," Mr Obama had said.
Mr Obama had appointed Mr Holbrooke as his special envoy for Afghanistan and Pakistan soon after he entered the white house in January 2009.
Since then, Mr Holbrooke has been instrumental in shaping the Af-Pak policy of the administration.
He has not only made innumerable trips to the region, but also to key countries across the globe with the core objective of defeating the al-Qaeda and the Taliban in Afghanistan, and bring lasting peace in the Af-Pak region.
White House's annual review of its Af-Pak policy is due later this week. Officials said his illness is unlikely to have any impact as the review was almost over when Mr Holbrooke fell ill.