A jubilant crowd cheered as Obama arrived on the podium with Chancellor Angela Merkel. Given the historic significance of the Brandenburg Gate over the course of the Cold War, the venue and timing of the speech were seen as particularly significant.

Obama began his sweeping, multi-themed address - in front of a crowd of some 6,000 vetted guests on Wednesday afternoon - by thanking his host Merkel.

He went on to note the hot weather. "It’s so warm," he said. "I feel so good that I'm actually going to take off my jacket and anyone else who wants to, feel free to do so."

Obama spoke of joy of the fall of the Berlin Wall, but warned that both the US and Germany should guard against complacency.

He repeated Kennedy's pledge of solidarity with the city, paying tribute to his predecessor, assassinated less than six months after his historic speech in Berlin. In particular, Obama praised Kennedy's call for "peace with justice," the central theme of his 1963 address.

"He lives forever as a young man in our memory but his words are timeless..." said Obama.

Perhaps most notably, the president said he would seek a reduction in the world's nuclear stockpiles, including a reduction in US and Russian arsenals.

"After a comprehensive review I have determined that we can ensure the security of America and our allies, and maintain a strong and credible strategic deterrent, while reducing our deployed strategic nuclear weapons by up to one third," he said. "I intend to seek negotiated cuts with Russia to move beyond Cold War nuclear postures,"

"We reject the nuclear weaponization that North Korea and Iran may be seeking," he said.

Obama also praised the efforts of Europe, and Germany in particular, in addressing global warming, saying that all nations should adopt that same approach and level of urgency. "We know we have to do more and we will do more," said Obama.

Mayor highlights 'shared values'

The president's speech was preceded by an address from Berlin Mayor Klaus Wowereit, who spoke of shared values. "This city of all cities knows the dream of freedom," said Wowereit. "It is this dream of freedom and solidarity that binds us as we walk into the future."

Merkel addressed the crowd immediately ahead of Obama, opening in a light-hearted manner. "We’ve chosen the best possible weather to welcome you warmly to Berlin," said Merkel.

The chancellor went on to talk about the fall of the Berlin Wall and the dream of German reunification being achieved. Merkel included a reference to President Ronald Reagan's 1987 appeal to Soviet leader Mikhail Gorbachev to "tear down this wall." She also spoke of German gratitude for the Berlin airlift in 1948, in which supplies were dropped to the then-blockaded city's residents by US and other Allied aircraft.

Before the speech, Obama had faced largely German-speaking journalists with Merkel and sought to reiterate the strategic importance of Germany and Europe for the United States as the global balance of power shifts.

Obama's last speech in Berlin was in 2008, when he was still a presidential candidate for the Democratic Party and before he was elected to his first term.

rc/dr (AFP, dpa, Reuters)