Former U.S. secretary of state, Alexander Haig, died on Saturday at a hospital in Baltimore at the age of 85.
His death was due to of complications linked to an infection, his family said.
President Barack Obama said he was a "great American who served our country with distinction".
"General Haig exemplified our finest warrior-diplomat tradition of those who dedicate their lives to public service," he went on.
Current Secretary of State Hillary Clinton said Haig had earned "the thanks of a grateful nation."
Haig, who was chief-of-staff under President Nixon during the Watergate scandal, and under his successor Gerald Ford, also served as NATO's Supreme Allied Commander before becoming secretary of state under President Reagan.
It was under Reagan that he suggested that the NATO doctrine allowed the use of nuclear weapons as a warning to the Soviet Union.
"There are contingency plans in the Nato doctrine to fire a nuclear weapon for demonstrative purposes, to demonstrate to the other side that they are exceeding the limits of toleration in the conventional area," he said.
He was defeated in his 1988 bid for the Republican Party presidential nomination by George HW Bush.
MOSCOW, February 20 (RIA Novosti)
