In a soaring speech delivered before tens of thousands of cheering Germans, Sen. Barack Obama, D-Ill., argued America has no better partner than Europe, and stressed the need for European troops in Afghanistan to help defeat the Taliban and al Qaeda.
"I come to Berlin as so many of my countrymen have come before. Tonight, I speak to you not as a candidate for president, but as a citizen -- a proud citizen of the United States, and a fellow citizen of the world," Obama said, standing before Berlin's famed Victory Column in Berlin.
At one point the crowd, estimated by Berlin police to number more than 200,000, burst into a chorus of "Yes we can!" -- Obama's campaign refrain in the United States.
"People of Berlin – people of the world – this is our moment. This is our time," he said.
Back home, the speech was greeted with much less enthusiasm by Obama's political rival, Sen. John McCain.
"I'd love to give a speech in Germany," McCain, R-Ariz., told reporters at a stop outside Columbus, Ohio. "But I'd much prefer to do it as president."
McCain visited Schmidt's Sausage Haus und Restaurant -- an intentional choice in a dig at Obama after the campaign's plans to visit an oil rig in the Gulf of Mexico were thwarted by Hurricane Dolly-related weather.
The presumptive Democratic nominee also argued that both European and American troops are needed in Afghanistan.
"This is the moment when we must renew our resolve to rout the terrorists who threaten our security in Afghanistan, and the traffickers who sell drugs on your streets," he said. Obama has called for more U.S. troops and NATO troops to be sent to Afghanistan.
"No one welcomes war," he said. "I recognize the enormous difficulties in Afghanistan. But my country and yours have a stake in seeing that NATO's first mission beyond Europe's borders is a success. For the people of Afghanistan, and for our shared security, the work must be done. America cannot do this alone. The Afghan people need our troops and your troops; our support and your support to defeat the Taliban and al Qaeda, to develop their economy, and to help them rebuild their nation. We have too much at stake to turn back now."
Obama has been greeted warmly in his first European trip as a presidential candidate.
A June Pew poll of global attitudes found the public in both Germany and France adore him -- 84 percent of Germans and 82 percent of French have more confidence in Obama than in McCain to deliver a positive change in U.S. foreign policy.
Addressing the anti-American sentiment prevalent in Europe during George W. Bush's presidency, Obama sought to paint a picture of a globe whose fate is intertwined.
"America cannot turn inward. That is why Europe cannot turn inward. America has no better partner than Europe. Now is the time to build new bridges across the globe as strong as the one that bound us across the Atlantic. Now is the time to join together, through constant cooperation, strong institutions, shared sacrifice, and a global commitment to progress, to meet the challenges of the 21st century," Obama said.
"Yes, there have been differences between America and Europe," he said, "But the burdens of global citizenship continue to bind us together. A change of leadership in Washington will not lift this burden. In this new century, Americans and Europeans alike will be required to do more -- not less. Partnership and cooperation among nations is not a choice; it is the one way, the only way, to protect our common security and advance our common humanity."
Obama added: "That is why the greatest danger of all is to allow new walls to divide us from one another."
The presumptive Democratic nominee argued terrorism is the common threat both Europeans and Americans share.
"The fall of the Berlin Wall brought new hope. But that very closeness has given rise to new dangers -- dangers that cannot be contained within the borders of a country or by the distance of an ocean," he said. "The terrorists of September 11th plotted in Hamburg and trained in Kandahar and Karachi before killing thousands from all over the globe on American soil.
The speech came after a meeting between Obama and German Chancellor Angela Merkel, in which they discussed the wars in Iraq and Afghanistan as well as climate and energy issues at Germany's chancellery.
They also discussed Pakistan, the Middle East peace process, the trans-Atlantic economic partnership, the global economy and "the need for cooperation on the international level and in international organizations to solve important global questions," a Merkel aide said.
Stakes were high going into Obama's planned speech in Berlin after a near-perfect overseas trip that many have tamped down fears of how Obama would handle U.S. foreign policy.
In advance of the speech, Obama told reporters: "Hopefully it will be viewed as a substantive articulation of the relationship I would like to see between the United States and Europe...I am hoping to communicate across the Atlantic the value of that relationship and how we need to build on that."
Obama flew to Berlin from the Middle East, where he had toured Jerusalem and met with Israeli and Pakistani leaders.
Closing his evening speech before a throng of Europeans who had gathered to see him, Obama said, "People of Berlin -- and people of the world -- the scale of our challenge is great. The road ahead will be long. But I come before you to say that we are heirs to a struggle for freedom. We are a people of improbable hope. Let us build on our common history, and seize our common destiny, and once again engage in that noble struggle to bring justice and peace to our world."
But even as Obama was greeted by enthusiasm overseas, not all were heeding the call at home, where the candidate will face voters in November.
"What has upset me is that he is over there acting presidential ... I don't want him over there representing me," Columbus, Ohio, resident Diane Woods said during McCain's visit.
"I don't know why Obama's getting all this attention," she said, "McCain is right where he should be -- in America."
ABC News' David Wright contributed to this report.