Holbrooke, a forceful presence in American diplomacy for more than 45 years, died in Washington, D.C., at the age of 69 last month.
Holbrooke was putting the finishing touches on a major report on American military and diplomatic efforts in Afghanistan, when he suffered a torn aorta and had to have emergency surgery.
He was in Secretary of State Clinton's office when he collapsed, and was rushed to George Washington University Hospital.
According to officials briefed on the matter, Holbrooke's final words were, "You've got to stop this war in Afghanistan."
"He served his country until his final moments," President Obama said today, referring to the diplomat's last words.
While Holbrooke wasn't always a popular figure in Afghanistan and Pakistan, where he was last tasked to work, his sudden death has left a void at a time that the U.S. struggles with an increasingly violent war in Afghanistan and a tense relationship with Pakistan's military.
"Richard was brilliant, blunt and he did fight until the very end for what he believed in," said Secretary of State Hillary Clinton.
ABC News' Joshua Miller and Nick Schifrin contributed to this report.