Answer:
The American diplomat who stressed the need to contain communism within its current borders was George F. Kennan.
Step-by-step explanation:
George Frost Kennan was an American diplomat, political scientist and historian whose ideas had a strong influence on US policy towards the Soviet Union at the end of World War II.
He is known in the political world for having partly created the concept of containment (this term designating measures to stem Soviet expansionism) and as a key figure of the Cold War.