US President Barack Obama and his German counterpart Joachim Gauck (L) meet with the 5th grade pupils of John F. Kennedy school outside Bellevue Castle in Berlin on June 19.

Obama will unveil plans for a sharp reduction in nuclear warheads in a landmark speech at the Brandenburg Gate on Wednesday that comes 50 years after John F. Kennedy declared "Ich bin ein Berliner" in a defiant Cold War address.  Reuters/Wolfgang Rattay