BRUSSELS (AP) Russia's ongoing confrontation with the West has ignited debate inside and outside the U.S.-led NATO alliance about what its responsibilities are, and how much of its time and effort should be spent to prepare for and if necessary counter Russian President Vladimir Putin's military ambitions.

Ian Lesser, senior director for foreign and security policy at the German Marshall Fund of the United States, said NATO must remain mindful of other modern security challenges, including cyberterrorism, threats to energy supplies and armed Islamic extremism.

But he predicted the trans-Atlantic alliance's focus will shift dramatically because of what he termed the biggest game changer in European security and defense environment in 20 years: Russia's armed aggression in Crimea and the Kremlin's continuing military pressure on Ukraine.

"Today we have a situation in which Russia and especially the Russian leadership is highly unpredictable," Lesser said. "There is something about the current crisis that suggests Russia is a rogue state, with all that would imply for deterrence and reassurance of allies."

As the alliance ponders how to react in Europe after years of fielding operations in the Middle East, Africa and Afghanistan, one of NATO's top commanders told The Associated Press that Russia's demonstrated ability to swiftly mobilize large numbers of troops in so-called snap exercises and Moscow's uncertain intentions have forced a rethink of NATO's capacity to respond and the deployment of its forces.

"What I am thinking about now is, is NATO correctly positioned and is it at the right state of responsiveness?" U.S. Air Force Gen. Philip Breedlove, NATO's supreme commander in Europe, said in a recent interview. "If we expect that Mr. Putin is going to be in charge of Russia for many years, if we are going to see this kind of exercise behavior in the future, are we prepared to react to the next snap exercise that goes across a border to impose its will on another sovereign nation in a different part of Europe? That's what I've been doing a lot of thinking about."

Already, NATO has reinforced its Baltic air patrols, put AWACS surveillance planes in the skies over Poland and Romania, dispatched warships to the Baltic and Black seas and sent 600 U.S. Army paratroopers to Poland and the Baltic states on temporary deployment.

Discussions are under way on longer-term measures, and how NATO must reposition, retool and otherwise react to the new challenge from Moscow will be the most pressing question on the agenda when President Barack Obama and leaders of the alliance's 27 other member nations gather for a summit in Wales this September.

During a visit to Canada this week, Breedlove said he wants the political leaders to think about permanently stationing alliance forces in Eastern Europe to reinforce local defense capabilities.

"I think this is something that we have to consider, and we will tee this up for discussion through the leaderships of our nations and see where that leads," Breedlove said Wednesday in Ottawa.

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NATO Flummoxed by Aggressive Russia