There is a legitimate reason for all this reluctance: No one knows how effective tougher sanctions would be. The mere threat of them has done nothing to stop the fighting in eastern Ukraine, which continues unabated -- as does the rise in Putin's personal approval rating (it hit asix-year high of 83 percent last week). With Russians in the grip of a nationalist fervor, why would Putin back down? And if he won’t, why put Europe’s businesses at risk?

These are the wrong questions to ask. It's true that sanctions alone may not persuade Putin to end his support of separatists in Ukraine. But there's a chance they might -- and even if they don't, they're still worthwhile.

One thing sanctions can do -- and there is some evidence they are hurting Russia’s economy already -- is deter future behavior. If Putin has unleashed a nationalist hunger to restore Russian dominance that he has lost either the will or the ability to control, all the more reason to cut off the arms and money that fuel further adventures, in Ukraine or elsewhere.

There are other reasons for sanctions, large and small: Cooperation and agreement on sanctions would help keep the EU united on other equally important issues, such as economic aid to Ukraine and ways to help the young presidency of Petro Poroshenko. Sanctions would show Europe is willing to stand up for the principles of sovereignty and democracy, which it claims to revere. And they would deprive Putin of the ability to play the U.S. and the EU off each other.

Finally, it is worth pointing out that sanctions are in Europe's long-term economic interest. The goal is not merely to deter Russia; it is to ensure the stability and vitality of the European economy. If Russia insists on using Europe's dependence on its energy to endanger the continent's security, then Europe needs to take steps to protect itself.

David Fuller's view

If Europe will not introduce shared sanctions of consequence, why would Putin stop with Ukraine rather than increase Russia’s dominance in other regions? It has happened before and Putin has made no secret of his regret that the Soviet Union no longer exists.