BERLIN, July 24 (Xinhua) -- U.S. presidential candidate Barack Obama called here on Thursday for stronger ties across the Atlantic Ocean.

    Obama made the call in his speech in front of the 226-foot high Victory Column, his first formal speech outside the United States.

German Foreign Minister Frank-Walter Steinmeier (L) and U.S. Democratic presidential candidate Senator Barack Obama meet members of the media in Berlin July 24, 2008.

"The walls between old allies on either side of the Atlantic cannot stand," Obama said, winning applause from over 100,000 crowds standing on the street the Berlin Wall once ran over.

    The Illinois Senator urged Europe and the United States to work together to "defeat terror and dry up the well of extremism that supports it."

U.S. Democratic presidential candidate Senator Barack Obama is surrounded by Secret Service agents as he boards an elevator at his hotel in Berlin, July 24, 2008

"The walls between the countries with the most and those with the least cannot stand. The walls between races and tribes, natives and immigrants, Christian and Muslim and Jew cannot stand," he said.

    Obama noted that America and Europe should unite more to tackle international issues like terrorism, the Middle East and Iran.

A street performer stands with U.S. flag in front of the Brandenburg Gate in Berlin July 24, 2008.

"No one welcomes war. 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," he said.

    "For the people of Afghanistan, and for our shared security, the work must be done. America cannot do this alone," he added.

    Obama also said Iran should "abandon nuclear ambition" and called for a "world without nuclear weapons," which won widespread cheers from crowds.

    Obama said he was speaking as a citizen, not as a president, but local media compared his speech to historic speeches in the same place by U.S. Presidents John F. Kennedy and Ronald Reagan.