Obama presses Europe on Afghanistan in Berlin

Relations between the United States and Germany reached a post-war low under Merkel's predecessor Gerhard Schroeder, who strongly opposed the U.S. invasion of Iraq in 2003.

"Yes, there have been differences between America and Europe. No doubt, there will be differences in the future," he said. "The greatest danger of all is to allow new walls to divide us from one another."

His comments were cheered by a huge crowd, some wearing Obama badges, t-shirts with the campaign slogan "Yes We Can" and carrying American flags. A reggae band played and people gulped down beer under clear skies in a summertime party atmosphere.

The loudest applause came when Obama talked about the environment, multilateralism and human rights, but his audience fell silent when he raised Afghanistan.

"Relations between Germany and the United States will improve under Obama," said Dennis Buchner, 31. "But he has high expectations of Germans increasing their military engagement in Afghanistan. That will certainly spark debate in Germany."

(Additional reporting by Kerstin Gehmlich, Madeline Chambers)

(Writing by Noah Barkin; Editing by Giles Elgood)