Obama, a first term Illinois senator, is planning a trip to Europe and the Mideast this summer to bolster his foreign policy credentials -- one of the strong points of his Republican opponent, John McCain, in the November election.

The German government has denied that Washington put pressure on Merkel to block the proposed Obama speech. German newspapers reported Bush administration officials had signaled their reservations about Obama speaking at the landmark.

A focal point of Cold War tensions, West Berlin was kept free during a Soviet blockade six decades ago by a U.S.-led Air Lift. Since then, American leaders from John Kennedy to Ronald Reagan and Bill Clinton have delivered major speeches in Berlin.