Russia could invade Ukraine at any time and might create a surprise pretext for an attack, the United States said on Sunday, as it reaffirmed a pledge to defend "every inch" of NATO territory.
Russia has more than 100,000 troops massed near Ukraine, which is not part of the Atlantic military alliance, and Washington - while keeping open the diplomatic channels that have so far failed to ease the crisis - has repeatedly said an invasion is imminent.
