Global challenges are pushing the EU toward an unavoidable dilemma. The EU ought to expand to include new countries and reach a critical size that will let it weather the 21st century. However, the EU has to also be a stronger, more unified political system whose functional feasibility depends on a limited number of countries in advanced economic and monetary convergence. The vicious circle of “a globally competitive, wider Europe” versus an “institutionally efficient deeper eurozone, with a limited number of countries” can only be broken by an innovative institutional engineering in adopting a progressive approach.