Mr Obama said he still took inspiration from the courage of East Germans
Below are remarks by world leaders and dignitaries attending the 20th anniversary of the fall of the Berlin Wall, which led to the reunification of East and West Germany.
GERMAN CHANCELLOR ANGELA MERKEL
Today marks a truly happy moment of German and European history. Twenty years ago the door to freedom opened up and a seemingly invincible wall that divided a people and an entire continent suddenly became permeable.
It was one of the happiest moments of my life.
FORMER SOVIET LEADER MIKHAIL GORBACHEV
My clairvoyant skills and those of (former German Chancellor Helmut) Kohl were up to nothing then. We did not think the wall would fall so fast.
US PRESIDENT BARACK OBAMA, IN A VIDEO ADDRESS
November 9, 1989, will always be remembered and cherished in the United States. Like so many Americans, I will never forget the images of people tearing down the wall. There could be no clearer rebuke of tyranny, there could be no stronger affirmation of freedom.
Few would have foreseen... that a united Germany would be led by a woman from (the east German state) Brandenburg or that their American ally would be led by a man of African descent. But human destiny is what human beings make of it.
US SECRETARY OF STATE HILLARY CLINTON
Now we have to turn our attention to the challenges of the 21st century. A wall, a physical wall, may have come down but there are other walls that exist that we have to overcome and we will be working together to accomplish that.
BRITISH PRIME MINISTER GORDON BROWN
The whole world is proud of you (the people of Berlin). You tore down the wall and you changed the world. You tore down the wall that for a third of a century had imprisoned half a city, half a country, half a continent and half the world. And because of your courage two Berlins are one, two Germanies are one and now two Europes are one.
FRENCH PRESIDENT NICOLAS SARKOZY
If I am happy to be here, it is because the fall of the Berlin Wall was a liberation, and the fall of the Berlin Wall serves for us all today as a call to fight oppression and to tear down all the walls that still separate the world, that divide cities, regions and nations.
This is the message that a unified Europe proudly embodies and delivers to the world. We are brothers, we are Berliners.
RUSSIAN PRESIDENT DMITRY MEDVEDEV
Here in Berlin, we all hope that the time of confrontation is in the past.
The unification agenda is very important for everyone. I hope we all have rejected the barriers that divided us before. Today, we would like to work on this agenda with you. Think about our children, think about our future, our Europe. This is very important for Russians as well.