President Obama on Wednesday called for the United States and Russia to reduce their arsenals of nuclear weapons by up to one-third, using a speech at the iconic Brandenburg Gate in Berlin to renew a long-stalled push for disarmament.

“We may not live in fear of nuclear annihilation, but as long as nuclear weapons exist, we are not truly safe,” Obama told a few thousand people at the heart of the German capital. “Peace with justice means pursuing a world without nuclear weapons, no matter how distant that dream may be.”

Obama’s proposal would reduce U.S. and Russian stockpiles of nuclear warheads to roughly 1,000 each, down from the 1,500 outlined in the current treaty between the superpowers. However, the plan faces an uphill battle with Russian President Vladimir Putin, who has repeatedly dismissed similar recommendations.

Obama made the announcement nearly 50 years to the day since President John F. Kennedy’s famous ‘”Ich bin ein Berliner’” Cold War speech and from the same site of President Ronald Reagan’s “Tear down this wall” address, looking to frame his nuclear appeal within a historic arc.

“Complacency is not the character of great nations,” Obama declared, speaking behind bulletproof glass, with sweat dripping from his face on a 91-degree afternoon.

German Chancellor Angela Merkel, who is facing a re-election challenge later this year, introduced Obama.

Though the president received a warm reception from the German crowd, it wasn’t nearly as exuberant as when then-candidate Obama visited Berlin five years ago. Obama on Wednesday addressed roughly 6,000 invited guests in a far more intimate setting than the 200,000 Germans who greeted him in 2008.

Cognizant of German skepticism about his commitment to civil liberties, Obama called again for the closure of the U.S. prison at Guantanamo Bay, Cuba, and defended top-secret phone and Internet surveillance programs that have drawn widespread criticism across the U.S. and Europe.

“It means balancing the pursuit of security with the protection of privacy,” Obama said of his counterterrorism efforts. “Our current programs are bound by the rule of law and they’re focused on threats to our security, not the communications of ordinary persons. They keep people safe in the United States and here in Europe.”

And Obama, who is expected next month to announce new methods for cracking down on carbon emissions, pledged to the European audience that he would not ignore the threat of climate change.

Obama’s speech in Berlin was the culmination of a three-day trip through Europe, which included the gathering of G-8 leaders at a summit in Northern Ireland. U.S. officials and their allies called for the end of the civil war in Syria and agreed to crack down on corporations setting up offshore tax havens, among other measures.