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Markus Schreiber, Pool, Associated Press
United States Secretary of State John Kerry, left, touches the remains of the Berlin Wall during a visits at the Wall memorial site prior to a news conference with German Foreign Minister Frank-Walter Steinmeier , third left, in Berlin, Wednesday, Oct. 22, 2014.

BERLIN — Surrounded by relics of the Cold War, U.S. Secretary of State John Kerry and his German counterpart warned Wednesday against a return to the bitter divide between east and west over the current crisis in Ukraine.

Under gloomy skies and a steady rain, Kerry and German Foreign Minister Frank-Walter Steinmeier visited one of the few remaining sections of the Berlin Wall. They emphasized that the West does not seek confrontation with Russia and implored Moscow to move quickly to fulfill the terms of an agreement to end the fighting in eastern Ukraine between the government and pro-Russian separatists.

Ukraine accuses Moscow of aiding the separatists, a charge that Moscow denies.

Ahead of next month's 25th anniversary of the fall of the Berlin Wall, Kerry and Steinmeier met German high-school students about the age that Kerry was when he lived in divided Berlin after World War II while his father served as a U.S. diplomat.

Though the Wall had not been built when Kerry rode his bicycle into the Soviet zone of the city as a 12-year-old, he recalled the stark contrast between east and west, visible in the clothing and demeanor of Berliners as well as the conditions.

"As a young child I saw the difference, I felt the difference," he told reporters after he and Steinmeier met the students and, with the wall behind them, chatted with a woman who had escaped East Germany by driving her Trabant car to Hungary.

"It frightened me enough that I turned back fairly quickly," Kerry said of his bicycle ride. "It was a difference between hope and despair, between light and darkness. You noticed it."

Kerry said he hoped the Ukraine crisis would not spark another Cold War and maintained that the West's tough stance against Russian intervention in Ukraine was only standing up for peoples' basic freedoms.

"These freedoms are still being threatened in too many parts of the world and they are even being threatened right here in Europe," he said. "Russia's aggression in Ukraine needs to end."

"We hope that Russia, with whom we do not seek conflict, with whom we would much rather be working together to deal with the problems of the world ... will understand how seriously the world takes the efforts to cross the lines of sovereignty and independence of a nation."

Germany has been leading efforts to find a diplomatic solution to the crisis in Ukraine, while also seeking to keep up pressure on Moscow with economic sanctions. Chancellor Angela Merkel has talked frequently with Russian President Vladimir Putin and met him in Italy last week.

"We know that this conflict is still explosive enough to threaten the peaceful order in Europe," Steinmeier said. "It is our responsibility to prevent a new divide in Europe opening up ever again."

"None of us want another generation growing up with the foreboding sense of a Cold War," Kerry added.

David Rising and Geir Moulson contributed to this story.