Richard Holbrooke, President Obama's special envoy to Afghanistan and Pakistan, died Monday following heart surgery.
Holbrooke, 69, had been in critical condition since undergoing 20 hours of emergency surgery that began Friday to repair a torn aorta.
A foreign-policy giant, Holbrooke will be best remembered for his work in the Clinton administration, when he brokered the 1995 agreement to end the war in Bosnia.
"He was one of a kind, a true statesmen, and that makes his passing all the more painful," Clinton said.
Holbrooke was meeting with Clinton on Friday when he became ill and was rushed to a hospital. He never recovered.
Clinton's statement said he died while surrounded Monday evening by his wife, Kati, his two sons, his stepchildren and other family members.
In a statement, Obama said Holbrooke had made America stronger, safer and more respected with his decades of foreign service, which began with his years of service working for the Kennedy and Johnson administrations in Vietnam.
Holbrooke worked on the Paris peace talks that led to the end of the Vietnam War, and helped normalize relations with China. He later served as ambassador to Germany after the fall of the Berlin Wall, and then as an assistant secretary of State for European and Canadian Affairs and U.S. ambassador to the United Nations.
"For nearly 50 years, Richard served the country he loved with honor and distinction," Obama said. "Like so many presidents before me, I am grateful that Richard Holbrooke was on my team, as are the American people."
In Obama's administration, Holbrooke took on the challenge of the Afghanistan war, and Obama on Monday night credited Holbrooke for progress in that fight.
"The progress that we have made in Afghanistan and Pakistan is due in no small measure to Richard's relentless focus on America's national interest and pursuit of peace and security," he said.
Speaker Nancy Pelosi (D-Calif.) praised Holbrooke's service. She tweeted: "Holbrooke was a strong fighter for peace — our country has lost a brilliant and respected diplomat."
The White House plans Thursday to publish the findings of a year-end review of the Obama administration's Afghanistan strategy.
Obama earlier on Monday described Holbrooke as "one of the giants of American foreign policy" in comments at the State Department. The president had visited with Holbrooke’s wife and others in the family earlier on Monday.
This story was posted at 7:51 and updated at 9:27 p.m.