Three years after Mario Draghi pledged to do whatever it took, within his mandate, to save the euro, the breakdown in the Greek rescue talks is calling into question the integrity of the entire currency union.
While Greece accounts for less than 2 percent of the eurozone's output, its exit would hurl the bloc into unknown territory by setting a precedent for other nations to reconsider their membership.
Greek Prime Minister Alexis Tsipras upped the ante just before the weekend by refusing to immediately accept creditors' conditions for extending aid beyond June 30 and instead calling a referendum on the proposals. The crisis threatens to undo much of the work that Draghi, president of the European Central Bank, has done to shore up confidence in the euro as a leading currency of global trade.