Mr. Obama should make clear that he will no longer shrink from applying sanctions to Russian leaders and businesses complicit in aggression or human rights violations. An expanded list of Russian officials subject to visa denials and asset freezes that was drawn up by the State Department late last year should be immediately approved by the White House. Russian officials in the chain of command of the Ukraine invasion, as well as Russian companies and banks operating in Crimea, should be the next targets of financial sanctions.

The most powerful non-military tool the United States possesses is exclusion from its banking system. Mr. Obama should make clear that if Russia does not retreat from Ukraine, it will expose itself to this sanction, which could sink its financial system. Russia’s economy, unlike that of the Soviet Union, is heavily dependent on Western trade and investment. It must be made clear to the Kremlin that the Ukraine invasion will put that at risk.