The founding of the two German states increased Cold War tensions. West Berlin was surrounded by East German territory, and East Germany proclaimed the Eastern part as its capital, a move the western powers did not recognize. East Berlin included most of the city's historic center. The West German government established itself in Bonn. In 1961, East Germany began to build the Berlin Wall around West Berlin, and events escalated to a tank standoff at Checkpoint Charlie. West Berlin was now de facto a part of West Germany with a unique legal status, while East Berlin was de facto a part of East Germany. John F. Kennedy gave his "''Ich bin ein Berliner''" speech on June 26, 1963, in front of the Schöneberg city hall, located in the city's western part, underlining the US support for West Berlin. Berlin was completely divided. Although it was possible for Westerners to pass to the other side through strictly controlled checkpoints, for most Easterners, travel to West Berlin or West Germany was prohibited by the government of East Germany. In 1971, a Four-Power agreement guaranteed access to and from West Berlin by car or train through East Germany.