FILE – In this June 3, 1961, file photo, Soviet Premier Nikita Khrushchev walks with U.S. President John F. Kennedy at the residence of the U.S. ambassador in Vienna, Austria. The notion of a substantive sit-down between North Korean leader Kim Jong Un and U.S. President Donald Trump Äì the most gazed-upon figures of this moment in the planet’s history Äìis a staggering prospect and a potential logistical nightmare if the two countries ever tried to make it happen. (AP Photo)