KIEV (Reuters) - U.S. Secretary of State Rex Tillerson said on Sunday that Russia must take the first steps to de-escalate violence in eastern Ukraine, adding that Washington’s primary goal is the restoration of Ukrainian territorial integrity. On a maiden official visit to Ukraine, Tillerson also said the United States would explore ways of changing the status quo in the Ukraine crisis, and said Russian interference in the 2016 U.S. election still impeded better relations with Moscow.    