the answer is: prevent and stop the spread of communism
They both designed a foreign policy denominated of containment towards Soviet expansion into Eastern Europe and central Asia. Some key points of tension where China, Korea, Africa, Vietnam, and later Latin America.
Officially with the Truman Doctrine, the American foreign policy was formulated to counter Soviet geopolitical expansion during the Cold War. It was sent to Congress by President Harry S. Truman on March 12, 1947, As conflicts emerged after Greece in Turkey. In 1947, England first requested the US to take the lead in supporting the pro-capitalist Greek government.
The relations with the Soviet communist bloc deteriorated soon after the WW2 leading to a global crisis that went on its height at 1962.