U.S. President Barack Obama has criticized Russia's "increasingly aggressive" stance on Ukraine, where fighting between pro-government forces and separatists has killed more than 6,100 people since April 2014.
Speaking after meeting with NATO Secretary-General Jens Stoltenberg at the White House on May 26, Obama said, "We had a chance to discuss the situation in Ukraine and the increasingly aggressive posture that Russia has taken."
He also urged Russia to "stop supporting separatists and to withdraw all its forces from eastern Ukraine," which continues to be embroiled in sporadic fighting despite a cease-fire agreement signed in Minsk in February.
Relations between Moscow and the West have dropped to their lowest point since the Cold War after Russia annexed Ukraine's Crimean Peninsula in March 2014.
Western countries and NATO also accuse Russia of backing rebels in Ukraine's east with troops and weapons, which Moscow denies.
With reporting by AFP