What was the issue between the western superpowers {US and Great Britain} against the Soviet Union over West Berlin?no

As part of the Potsdam agreement soon after the end of World War II in Europe, Germany was divided into four zones of occupation for the French, the British, Americans and Soviets.  Berlin, even though it was in the eastern zone, was also divided among these four powers. 

After ten years, the agreement stated that all foreign forces would pull out and democratic elections would be held.  The Soviets never left, and installed a communist government with East Berlin as its capital.

West Berlin remained connected to West Germany by highways and railways, and the Soviets refused to supply the west part of the city.  In 1948, in the early days of the Cold War, the Soviets blockaded West Berlin.

If Britain and America gave in and let the city fall into Soviet hands, then that sent a message that western Europe was vulnerable.  We adopted a policy of containment and airlifted supplies into West Berlin rather than surrender it, and rather than start World War III to defend it.  This episode became a model for containment during the Cold War.