By David Lawder and Pavel Polityuk WASHINGTON/KYIV (Reuters) – 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. Moscow denies any such plans and has accused the West of “hysteria”. German Chancell…