Days after his ally Viktor Yanukovych was ousted as Ukraine's leader, Russian President Vladimir Putin ordered a 150,000-troop Russian military exercise on Ukraine's border. The fall of Yanukovych — and Putin's potential response to it — has reignited a debate in Washington on how to respond to the assertive Russian leader.

For Obama administration officials, Vladimir Putin is a concern but not a threat. Any talk of renewed Russian-American rivalry like during the Cold War, they say, is reckless and counterproductive.

"This is a world where we need to work with the Russians," a senior State Department official said Tuesday. "This is not about the United States versus Russia."