Germany hailed the strength of transatlantic ties Wednesday on the 50th anniversary of US president John F. Kennedy's stirring Cold War declaration "Ich bin ein Berliner", with celebrations across the reunited city.
Foreign Minister Guido Westerwelle said JFK's historic 1963 speech to 450,000 people outside West Berlin's town hall remained "unforgettable for us Germans".
"President Kennedy gave Berliners new hope in difficult times and all Germans new confidence," he said as the city commemorated the event with tours, lectures, exhibitions, new book publications and a ceremony at the speech's venue.
Westerwelle said a visit to Berlin last week by President Barack Obama, in which he borrowed tropes from Kennedy's speech to call for stronger transatlantic cooperation on global crises, showed that the spirit of the pledge was still relevant.
"Shared history has become vibrant German-American friendship, which in a world of fundamental change is as important today as it was then," he said.
Speaking later at the town hall in the western district of Schoeneberg, Berlin Mayor Klaus Wowereit said the relationship between the United States and a more powerful, unified Germany had matured and deepened since that heady summer day.
"The America-enthusiasm of an earlier age has become closeness and trust," he said. "For our globalised and Internet-using youth, America is no longer the promised land bar none. The world has grown bigger."
The commemoration began with the ringing of the town hall's Liberty Bell, a gift from the US just five years after World War II, and included musical performances and recitations from the speech by students from Berlin's bilingual John F. Kennedy School.
The director of Boston's JFK Presidential Library, Thomas Putnam, said the message of the address had "lit a fire throughout the world".
"That desire for liberty and self-determination would inspire millions including a freedom fighter imprisoned on Robben Island, a union leader from Gdansk, a jailed poet in Prague, a fearless protester in Tiananmen Square and a native daughter of Burma living under house arrest," he said.
Kennedy's eight-hour visit came at a critical stage of the Cold War, and Berlin was on the front line.
It was only a year since the United States and Soviet Union nearly went to war in the Cuban missile crisis, and two years after East Germany's communist regime erected the Berlin Wall, cleaving the city in two.
In an electrifying 10-minute address, Kennedy gave Berliners what they wanted to hear: a condemnation of the Wall and a promise that the free world stood by them.
"Freedom has many difficulties and democracy is not perfect but we have never had to put a wall up to keep our people in, to prevent them from leaving us," the defiant president said, in a firm rejection of communist appeasement.
At the end, Kennedy uttered the immortal words: "All free men, wherever they may live, are citizens of Berlin and therefore, as a free man, I take pride in the words 'Ich bin ein Berliner' (I am a Berliner)."
His vow, just five months before he was assassinated in Dallas, was greeted with rapturous applause from the crowds of Berliners thronging the square.
Egon Bahr, an advisor to then West Berlin mayor Willy Brandt, said Germans instantly understood the message of Kennedy's "explosive" words, calling them "an unwritten pact" with Soviet leader Nikita Khrushchev.
"Berliners knew instinctively that they could feel safe," said Bahr, 91.
"That was the purpose of the speech -- afterwards there would never again be a (Cold War) crisis involving Berlin, involving Germany, involving Europe. There was to be no war, and no change in the status quo, and it was intended to allow us to bridge the time. And it held the whole time Germany was divided."
The last communist leader of East Germany, Egon Krenz, admitted that the Berlin Wall would never have withstood the power of the Internet to foment dissent and link up pro-democracy activists.
"The Wall would have been no match for Facebook," he told weekly newspaper Die Zeit. "That much is clear."