(Washington, D.C.) -- The White House national security adviser is urging Russia to de-escalate its troop presence on the border with Ukraine. Jake Sullivan spoke with his Russian counterpart during a phone call Monday. A White House statement of the call says that Sullivan "indicated U.S. readiness to engage in diplomacy" while making clear any dialogue must take place in full coordination with European Allies and partners. This is the second time Sullivan has spoke with Russian President Vladimir Putin's foreign policy adviser in an attempt to ward off a Russian invasion of Ukraine. Russia has demanded NATO not expand to include Ukraine, but NATO officials have refused to rule out the country joining the alliance in the future.