But can the EU retain its present level of cohesion if it extends membership to as many as 10 new countries? The organization is already facing challenges in integrating the 10 countries it admitted last year.
A jubilant Croatian Prime Minister Ivo Sanader had no doubt this week that EU expansion will encompass his whole region.
"We want to assist and to help our region and our neighbors to achieve their goals, and I'm sure the sooner Croatia becomes a full member of the EU, the sooner Serbia-Montenegro, Macedonia, Albania, Bosnia-Herzegovina, and all others [will become members]," Sanader said.
Balkan neighbors Romania and Bulgaria are already set for membership in 2007.
In light of continued expansion in the next decade, the concept of "an ever-closer union" among European states -- a stated goal of the EU -- appears to be faltering, at least in the medium term.
Political analyst Peter van Hamm of the Netherlands Institute of International Relations said the EU is going "very fast and very far."
"It is very difficult to reach consensus and to move forward with such a large group," van Hamm said.
Several factors have slowed the pace of integration. A new draft constitution was painstakingly hammered out in order to streamline the union's cumbersome process of decision making, so that it would not be paralyzed by the foreseen near-doubling of its membership.
But French and Dutch voters rejected the new EU constitution in referendums earlier this year. The unexpected result was a major setback for European integration. Moreover, it made painfully clear the depth of voter unhappiness with current EU policy.
Public fear of cheap labor from Eastern Europe and Turkey flooding their jobs markets is thought to have led many to vote against the constitution. Globalization is accelerating the pace of change and disconcerting Europeans, unsure of where exactly Europe is heading, and whether it will ensure them a secure future.
Another key development is the loss of Germany and France's traditional role as the two "engines" driving EU integration.
In Germany, slow economic growth has depleted once-brimming state coffers. Faced with growing national debt, Berlin is no longer prepared to smooth over EU troubles by footing the bill. Chancellor Gerhard Schroeder, the first postwar leader to have no memory of the Hitler years, has steered the union's traditional paymaster toward a more self-assertive policy.
Since the rejection of the constitution, France can no longer lead by example. Even earlier, France had angered Eastern European members by its peremptory suggestions that they should follow its lead in foreign policy, particularly in regard to ties with the United States.
However, analyst van Hamm pointed to a positive development in terms of groups of EU states working together on a "project."
"It is to some extent heartening to see the big three [France, Germany, and Britain] together with the [European] Commission taking the lead in dealing with Iran, that's a novelty, we haven't seen that [sort of grouping] in the past, the interesting thing is that it seems to be accepted by the rest of the EU member states as an potentially effective and quite efficient mechanism," van Hamm said.
The way the trio is negotiating with Iran over its controversial nuclear program could serve as a model for EU action in other international issues, allowing the EU to have greater influence in the future.