American and European officials are struggling to devise a response as Russia bears down on Ukraine, searching for new measures that will have more impact than the economic sanctions imposed so far, without risking major damage to their own industries or a military escalation that could spiral out of control. The officials are meeting this week to assemble a new package of sanctions targeting Russia’s banking, energy and defense sectors, but expressed skepticism that the measures would force Moscow to reverse course. President Obama faced rising calls from advisers and from Congress to move beyond economic actions to provide arms and more intelligence to Ukraine’s beleaguered military. The frustration at the inability to deter Moscow follows a shift on the battlefield, where Russian troops have turned the tide in favor of Ukrainian separatists. President Vladimir V. Putin of Russia, who last week suggested “statehood” for parts of […]