President Barack Obama and European Union leaders presented a unified front, promoting transatlantic trade as an antidote to Russia's influence in the region and a way to help Europe become less dependent on Moscow for energy.
Obama said that if Russian leaders thought they could drive a wedge between Europe and the United States, "they clearly miscalculated".
He spoke during a news conference at the Council of the European Union, after a working lunch with European Council President Herman Van Rompuy and European Commission President Jose Manuel Barroso.
Earlier Obama also made a solemn pilgrimage to a first world war cemetery.
"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." Obama joined Belgian Prime Minister Elio Di Rupo and King Phillipe in laying a trio of wreaths at a stone monument.