US President Barack Obama has said the United States needed a strong, united Europe to maintain international order.
Speaking in Germany, Mr Obama urged European allies to increase defence spending to address the so-called Islamic State group and other security threats.
Wrapping up a trip that has focused on boosting trade ties, the US leader pleaded with Europeans to look past the multiple crises facing their nations and maintain the unity that had brought peace to their continent.
His comments came after an earlier trip to London, where he urged Britain to stay in the 28-nation European Union, boosting efforts by Prime Minister David Cameron to avoid a "Brexit".
"I've come here today to the heart of Europe to say that the United States and the entire world needs a strong and prosperous and democratic and united Europe," Mr Obama said during a visit to a trade fair in the northern Germany city of Hanover, drawing applause from his audience.
Mr Obama said worries over Russia's annexation of Crimea and slow economic growth, particularly in southern Europe, had led to questions about integration on the continent and sparked destructive politics that stoked fears about immigrants and people with different religions.
An influx of migrants fleeing the civil war in Syria has heightened tensions within the bloc and put pressure on German Chancellor Angela Merkel, whose initial open door policy hurt her domestic political standing.
Mr Obama's visit to the trade fair was seen as a sign of support for a leader with whom he has forged close ties ahead of German elections next year.
The trip also allowed him to put his support for Ms Merkel and Mr Cameron in the wider context of Europe's role in the world.
"This is a defining moment, and what happens on this continent has consequences for people around the globe," Mr Obama said.
"If a unified, peaceful, liberal, pluralistic, free-market Europe begins to doubt itself, begins to question the progress that's been made over the last several decades, then we can't expect the progress that is just now taking hold in many places around the world will continue."
Mr Obama needs support from European allies to handle foreign policy challenges in Russia and the Middle East, and he used his platform in Hanover to announce deployment of an additional 250 US forces to Syria.
