Barack Obama returns to his message of hope, tempered by the years of experience

As a bead of sweat twinkled on the president's brow, he shrugged off his jacket mid-speech with the words: "We can be a little more informal among friends." In shirtsleeves, Barack Obama delivered an appeal to spread Western democratic values on a global scale, invoking the spirit of John F Kennedy as well as quoting his famous declaration of solidarity with an embattled Berlin.

There were just 4,500 "friends" gathered to hear the US president on a sweltering summer afternoon, compared with the estimated 200,000 who had turned out to watch the then Democratic nominee give a landmark, impassioned address in the German capital five years ago. This time around, his language was more measured, warning that "complacency is not the character of great nations".

The theme of hope remained, but there was also a concrete promise to reduce strategic nuclear weapons by a third and defensive words about the use of drones and the National Security Agency's surveillance programmes. Speaking behind bulletproof glass on the eastern side of the Brandenburg Gate - once part of the desolate "death strip" patrolled by East German border guards - he quoted from JFK's 1963 speech in West Berlin to warn against complacency and rally a coalition against global injustice. T

o applause, he repeated the famous words "Ich bin ein Berliner", but reminded his audience that Kennedy had urged Berliners to look to the future and think of all mankind. "Today, people often come together in places like this to remember history - not to make it," he told the crowd. "After all, we face no concrete walls, no barbed wire. And so sometimes there can be a sense that the great challenges have somehow passed. "If we lift our eyes as President Kennedy calls us to do, then we'll recognise that our work is not yet done. So we are not only citizens of America or Germany, we are also citizens of the world."

The president compared Afghans taking charge of their own futures or the Burmese emerging from dictatorship to Berliners who had "carved out an island of democracy". "They are who you were. They deserve our support, for they too, in their own way, are citizens of Berlin." The sole firm pledge in the speech was to reduce deployed strategic weapons by a third, cutting the number of US warheads to 1,000.

To applause, he said: "I intend to seek negotiated cuts with Russia to move beyond Cold War nuclear postures." The president said he would work with Nato allies to seek "bold reductions" in US and Russian tactical weapons in Europe. Obama said that America would host a summit in 2016 to continue efforts to secure nuclear materials, and reduce the threat of nuclear terrorism. At the G8 summit, the US and Russia signed a new agreement on securing nuclear material left over from the Cold War.

However, his arms reduction pledges were rejected by Russia's deputy prime minister. Dmitry Rogozin told the state-owned news agency ITAR-TASS that his country could not take this proposal seriously while the US was developing a missile defence system with the potential to intercept Russian weapons. In language reminiscent of his 2008 speech, Obama also spoke of the urgent need to confront climate change.

"With a global middle class consuming more energy every day, this must now be an effort of all nations, not just some," he said. "For the grim alternative affects all nations - more severe storms, more famine and floods, new waves of refugees, coastlines that vanish, oceans that rise."

When Obama was last here, he arrived as the alternative to an American president who was unpopular with many in Europe. Five years ago, in his speech at the Siegessaule, the column topped with a gold statue of the goddess of victory which is linked by a mile-long avenue to the Brandenburg Gate that was swamped with supporters, Obama drew loud applause for saying that no one nation could solve the world's problems alone. This time, he called for a revival of individual activism that would strengthen citizens in the developing world.

"Our efforts have to be about more than just charity. They're about new models of empowering people - to build institutions, to abandon the rot of corruption, to create ties of trade, not just aid, both with the West and among the nations that are seeking to." Obama touched on the issues that have clouded his presidency in the eyes of many of his liberal followers. He told the crowd of the need to move beyond "a mindset of perpetual war".

"In America, that means redoubling our efforts to close the prison at Guantanamo," he said. "It means tightly controlling our use of new technologies like drones. It means balancing the pursuit of security with the protection of privacy." But his rhetoric soared once more as he returned to the subject of Berlin's tumultuous past: "The wall belongs to history. But we have history to make as well." The mood in Germany remains generous towards Obama. In its cover story on the president this week, the news magazine Der Spiegel observed:

"The transatlantic friendship has grown less emotional, but also distinctly less narrow, and therefore more adult, more pragmatic." Data released by the Pew Research Center shows 88% of Germans say they still have confidence in Obama to do the right thing, compared with 14% for in George W Bush during his last year in office. For many in the crowd, the old magic was still there.

Leyla Schoen, a librarian, said: "He's a brilliant orator who used the right buzzwords. I was enthralled. He was against nuclear weapons. He wanted prosperity for all. But day-to-day politics is another matter." In 2008, Ms Schoen had watched his Berlin speech on TV. "That was more of an awakening," she said. "He kept saying 'we want', 'I would like'. Now there's more reality."