US President Barack Obama has laid a wreath at the World War I memorial at Flanders Field, noting the war that tore apart Europe still echoes in conflicts 100 years later.
"The lessons of that war speak to us still," Obama said on Wednesday in his first stop since arriving in Belgium late on Tuesday.
The president is in Brussels for a summit with European Union leaders.
He's also slated to meet with NATO's secretary-general and deliver a speech at the Palais des Beaux-Arts.
The itinerary, like much of Obama's European trip this week, is expected to be dominated by talk of a new threat on Europe's doorstep.
Obama and European leaders are to discuss Russia's armed seizure of the Crimean peninsula and how the West can prevent Moscow from moving further into Ukraine.
On Tuesday, Obama repeated threats of more painful economic sanctions if Russian President Vladimir Putin sends troops into other regions of the former Soviet state.
But the president also acknowledged that, for now, Crimea is likely to remain in Russian control.
"There's no expectation that they will be dislodged by force," he said in a news conference in The Hague.
Still, Russia's neighbours are looking for assurance that NATO will make good on its obligations to defend them.
Other European nations are worried about the effect that broader sanctions would have on their own fragile economies.
Obama's remarks later on Wednesday are expected to address such concerns, while avoiding the divisive and dated rhetoric of the Cold War era, officials have said.
The president's visit comes 100 years after the outbreak of World War I, an anniversary being widely marked in Europe.
In a morning ceremony at the cemetery west of Brussels, Obama, Belgian King Philippe and Belgian Prime Minister Elio Di Rupo placed wreaths at a monument erected to the missing dead.
In remarks afterward, all three leaders made reference to lessons of the war that apply today.
"Our countries have learned the hard way that national sovereignty quickly reaches its limits when met with heavily armed adversaries," said the king, who noted that his great-grandfather, King Albert, fought in the war.
Di Rupo warned that "those who ignore the past are taking the risk to relive it."
Noting that chemical weapons were used to "devastating effect" on Flanders Field, Obama said that today, in Syria and elsewhere, the world still struggles to eradicate their use.
"We thought we had banished their use to history, and our efforts send a powerful message that these weapons have no place in a civilised world. This is one of the ways that we can honour those who fell here," Obama said.
"This visit, this hallowed ground, reminds us that we must never, ever take our progress for granted."
