Holbrooke, 69, underwent additional procedures Sunday to improve blood circulation, but he remained in critical condition at George Washington University Hospital.
The president's diplomatic point man on the Afghanistan war, Holbrooke was stricken Friday while at the State Department and was rushed to the hospital, where he underwent more than 20 hours of surgery to repair the tear and bleeding in his aorta.
The State Department said Sunday that he received calls from Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari. As President Barack Obama's special envoy to Afghanistan and Pakistan, the longtime diplomat has made numerous visits to the region.
Holbrooke was meeting with Secretary of State Hillary Rodham Clinton about midmorning Friday when he fell ill, collapsed and was rushed to the hospital a few blocks away.
"Many people would have succumbed to that. Richard is fighting through," Obama adviser David Axelrod told CNN's "State of the Union" on Sunday. "Anyone who knows him, and I was with him Friday morning before this happened, knows how tough and resilient he is, and we're all praying that that quality sees him through now."
A torn aorta is a condition in which a rip develops in the inner wall of the body's largest artery allowing blood to enter the vessel wall and weaken it. If not corrected the condition can lead to rapid death. As blood enters the wall it reduces blood flow just as though there were a severely bleeding wound, leading to serious internal bleeding, a loss of blood flow and possible complications in organs affected by the lack of blood, according to medical experts.
While doctors were said to have stabilized Holbrooke's condition, recovery is likely to be lengthy.
Holbrooke's illness comes just days before the Obama administration is expected to roll out the results of its review of the Afghanistan war, on Thursday.
Gen. David H. Petraeus, commander of U.S. and NATO forces in Afghanistan; Mark Sedwill, NATO's senior civilian representative; and Ashraf Ghani, special adviser to Karzai, said in a joint statement that they "wish him a full and fast recovery."
Holbrooke's prolonged absence could effect the administration's ability to put in place - and also sell to a skeptical Congress - its push for Afghan forces to assume a greater role in the fighting, allowing U.S. troops to come home. It is a transition in which Holbrooke was expected to play an important part.
The feisty and sometimes abrasive diplomat - whose forceful style earned him nicknames such as "The Bulldozer" or "Raging Bull - is perhaps best known for helping broker the Dayton accords, a 1995 agreement that ended the war in Bosnia.
He served as ambassador to the United Nations during the Clinton administration. He also was ambassador to Germany from 1993 to 1994 and then assistant secretary of state for European affairs.