ANATOLII STEPANOV/AFP via Getty Images(NEW YORK) After weeks of mounting tensions, United States officials have warned that a Russian attack on Ukraine could happen "any day now." Russia has spent weeks building up military forces near eastern Ukraine, with more than 150,000 troops encircling Ukraine in Belarus and on the Russian side of the border, according to U.S. officials. The Kremlin has denied warnings of an imminent invasion and claimed in recent days that it is withdrawing some troops, while U.S. and NATO officials have said and commercial satellite images have shown there have been no signs of de-escalation. As global leaders continue to engage in diplomatic efforts to avoid war between Russia and Ukraine, a senior Department of State official told ABC News warned Thursday that this is "perhaps the most perilous moment for peace and security since the end of the Cold War." As the conflict plays out on a global stage, Americans are somewhat mixed on h