Barack Obama arrived for his first visit as US president to Berlin on Tuesday for talks with German Chancellor Angela Merkel and a major open-air speech at the city's Brandenburg Gate.
Obama arrived at Berlin's Tegel Airport from Northern Ireland where he and Merkel took part in a G8 summit dominated by the bloodshed in Syria and a bid by the European Union and the United States to create the world's biggest free trade area.
The 24-hour visit comes nearly 50 years to the day after John F. Kennedy's "Ich bin ein Berliner" solidarity pledge to the embattled western sectors of the city.
Merkel, the EU's most influential leader as the bloc grapples with a crippling debt crisis, is keen to discuss prospects for the trade pact, the so-called Transatlantic Trade and Investment Partnership.
And the chancellor, facing a general election in September, has vowed to seek answers from the president on revelations of secret US Internet surveillance.
The news this month struck a raw nerve in Germany, where memories of state snooping under the Nazi and communist dictatorships are still alive in the national consciousness.
Activists have registered with police to stage demonstrations on Wednesday, ranging in size from 50 to 500, against the US National Security Agency's practices.
Merkel said in a television interview Monday that US tips had helped Germany foil terror plots, including a 2007 bid to bomb US interests in the country.
But she said she would ask Obama the extent to which Germans' online communications were also being sniffed out.
"We have to be clear -- what is being used, what is not being used," she said.
The visit, on which Obama is accompanied by his wife Michelle and two daughters, will also feature a set-piece speech to 6,000 invited guests in front of the Brandenburg Gate, the symbol of German unity.
Obama was making his third visit to Germany, Europe's top economy, since taking office in 2009 but his first to the reunited capital since a triumphant visit as a candidate.
During that 2008 stopover, he drew a rapturous reception from a crowd of 200,000 with a pledge for a new chapter in transatlantic relations.