George F. Kennan, the key architect of the US policy of containment of the former Soviet Union during the Cold War, died on Thursday night in Princeton, New Jersey at the age of 101, US media reported Friday.

A foreign service officer from 1926 to 1953, Kennan also was a student of Russian history, a keen and intuitive observer of people and events and a gifted writer.

His great moment as a policymaker came in 1946. While serving in the US embassy in Moscow, he wrote a cable that outlined positions that guided Washington's dealings with the Kremlin until the collapse of the Soviet Union nearly half a century later.

Know as the Long Telegram, it said that Soviet expansion must be halted and spelled out how that could be done. Moscow is "impervious to the logic of reason," Kennan said, but "it is highly sensitive to the logic of force."

The telegram did not state, however, that war was inevitable. The policy should have a military element, Kennan maintained, but it should consist primarily of economic and political pressure.

"It is clear that the main element of any United States policy toward the Soviet Union must be that of a long-term, patient but firm and vigilant containment of Russian expansive tendencies," he once wrote.

Kennan's proposal became the foundation of the Cold War, which governed relations between the United States and the Soviet Union until the fall of the Berlin Wall in 1989.

The policy resulted in both the creation of the NATO alliance in 1949 and the Vietnam War of the 1960s.

Kennan's influence was diminished in 1949 with the appointment of Dean Acheson as secretary of state, who took a more aggressive stance towards Moscow.

He spent the rest of his years at the Institute for Advanced Study in Princeton, writing and lecturing, meanwhile serving as ambassador to Yugoslavia during 1961-1963.

Among some 20 books he authored were a history of US-Soviet relations in 1956 and his memoirs in 1967, both of which won the Pulitzer Prize.