WAREGEM, Belgium — President Barack Obama reached back 100 years to reinforce the U.S.-European bond, calling for a recommitment to peace today during a solemn pilgrimage to a World War I cemetery as European tensions run high over Russia’s incursion into Ukraine.

“This visit, this hallowed ground, reminds us that we must never ever take our progress for granted,” Obama said at Flanders Field American Cemetery and Memorial in northwest Belgium. “We must commit perennially to peace, which binds us across oceans.”

Followed by the stirring sound of a bugler playing taps, Obama joined Belgian Prime Minister Elio Di Rupo and King Phillipe in laying a trio of wreaths at the white stone monument at the center of the cemetery, the site of a significant World War I battle. The three leaders then walked among some of the white crosses that mark the burial site of 368 American troops, most of whom gave their lives in liberating Belgium from German occupation.

The Belgian leaders did not mention Russian President Vladimir Putin by name in remarks afterward, but clearly were referencing his audacious annexation of Crimea as they recalled the lessons of world war. “Our countries have learned the hard way that national sovereignty quickly reaches its limits” when confronted with armed adversaries, who don’t respect that sovereignty, said King Phillipe.

“We have to continue to draw lessons from the terrible war that started 100 years ago,” Di Rupo said. “And, above all, we have to prevent new conflicts.”

Obama came to Brussels to shore up commitments he received from allies in The Hague, Netherlands, to reassure Eastern European members of NATO that the alliance will stand by them and to make a larger point about European security a quarter-century after the fall of the Iron Curtain. He held a working lunch with European Union officials and later was to meet with NATO Secretary General Anders Fogh Rasmussen, embracing the alliance born as a bulwark against the Soviet Union.

The president, stepping up the task of solidifying broad-based support against Russia, dismissed Russia a day earlier as a mere “regional power” that was threatening its neighbors “not out of strength, but out of weakness.” He said that as president, he worried more about a nuclear device in Manhattan than he did about Russia.

It was the kind of brush-off-your-shoulder language sure to antagonize the nationalistic Putin, but it also belied the time and energy Obama and European leaders have devoted to isolate Russia and fashion a menu of sanctions designed to stop Moscow’s aggression.

Obama’s stewardship of U.S.-European relations has been hurt by revelations of communications prying by the U.S. National Security Agency.