One year after President Obama rallied core allies to join the United States in punishing Russia for its bellicose ways, he will use a gathering on Sunday of the world’s largest industrialized democracies to urge them to stand strong, and together, in isolating the Russian president, Vladimir V. Putin.
But this time, Mr. Obama faces an additional challenge: It is not entirely clear that their efforts are working.
The tough economic sanctions that have been the linchpin of American and European efforts to confront Moscow over its annexation of Crimea last year and its continuing aggression in Ukraine have, along with the lower price of oil, exacted a toll on Russia. They may even have helped deter Mr. Putin from escalating his intervention.
But they evidently have not forced him to give up his designs on Ukraine or to surrender Crimea, and many analysts believe he is playing a waiting game on the assumption that he can outlast Euro-American solidarity.