<P> Khrushchev had become emboldened upon seeing US President John F. Kennedy 's youth and inexperience show as weakness against Khrushchev 's brutal , undiplomatic aggression . This feeling of miscalculation and failure is admitted by Kennedy in the U.S. ambassador 's residence with New York Times columnist James `` Scotty '' Reston . Kennedy made the regrettable error of admitting that the US would not actively oppose this action in the Soviet sector of Berlin . On Saturday , 12 August 1961 , the leaders of the GDR attended a garden party at a government guesthouse in Döllnsee , in a wooded area to the north of East Berlin . There Ulbricht signed the order to close the border and erect a wall . </P>
who was the leader of the soviet union when the berlin wall was built
Khrushchev