NATO's secretary-general said Wednesday that Russia's intervention in Ukraine posed the most serious threat to Europe's security since the end of the Cold War and warned Moscow it would face international isolation.
"This is a wake-up call," alliance chief Anders Fogh Rasmussen said in prepared remarks. "For the Euro-Atlantic community. For NATO. And for all those committed to a Europe whole, free and at peace."
There had been crises in the Balkans in the 1990s and in Georgia in 2008, "but this is the gravest threat to European security and stability since the end of the Cold War," he said.
The situation was more serious because of the scale of Russia's action, representing one of the largest troop movements in Europe for "many decades," and because it was occurring "right on NATO's border," he said.
Rasmussen, who was holding talks in Washington on the crisis, denounced Russia's actions as "military aggression" that violated Ukraine's sovereignty.
"Any attempt to justify the annexation of Crimea through a so-called referendum held at gunpoint is illegal and illegitimate," according to the prepared remarks.
He demanded Moscow halt all military activities against Ukraine and seek a peaceful dialogue with Ukraine's government.
But "if it continues on its current course, Russia is choosing increased international isolation," said Rasmussen, in a reference to threatened economic sanctions against Moscow.
But Rasmussen issued no military threat and acknowledged the West had no "easy" options at hand.
"There are no quick and easy ways to stand up to global bullies.
"Because our democracies debate, deliberate, and consider the options before taking decisions. Because we value transparency and seek legitimacy for our choices.
"And because we see force as the last, not the first, resort."