WASHINGTON (AP) — For President Barack Obama, Russia’s aggressive annexation of Crimea is testing central tenets of his foreign policy philosophy: his belief in the power of direct diplomacy, his preference for using economic sanctions as punishment and his inclination to proceed cautiously in order to avoid creating larger long-term problems.

The question facing the White House now is whether actions that have done little to stop Russia from claiming Crimea are tough enough to stop further escalations by Moscow. And if they continue to prove insufficient, what else is Obama willing to do to change Vladimir Putin’s calculus?