The presence of Russian troops in Ukraine 's Crimea has ratcheted up tensions . Comment: A military response is n't considered to be a realistic possibility . The crisis is roiling global markets , pushing up the price of oil and hurting the ruble .
The presence of Russian troops in Ukraine 's Crimea has ratcheted up tensions . U.S. President Barack Obama appears to have limited options to pressure Russia . A military response is n't considered to be a realistic possibility . The crisis is roiling global markets , pushing up the price of oil and hurting the ruble .