A woman takes a photo with her mobile phone of the lights on the Agbar Tower Friday in Barcelona, Spain. The tower's lights say 50

Berlin ? After the outrage and cussing subsided, you could almost hear the national chuckle over a proposal by the European Union that Germany post speed limits on 3,700 miles of autobahn as a way to reduce carbon dioxide emissions.

This nation cherishes cheek-rippling speed; vast stretches of the autobahn are sacred ribbons of blacktop where how high you can rev an engine is bound only by the laws of physics. But Germany is also a member of the EU, which leads to the question: How does a country keep its identity while swearing allegiance to the spirit of something larger?

That dilemma is at the core of the EU, which celebrates its 50th anniversary Sunday partly as a success story and partly as a grand but unfinished vision. Founded as an economic pact by six Western European capitals after World War II, the EU today has 27 member states, a population of nearly 500 million and an economy that is as large, but not as strong, as that of the United States.

It has loosened borders, calmed nationalist sentiments that had inspired centuries of bloodshed, and introduced a single currency, the euro. Despite these achievements, the EU is viewed by many people as an aloof, bureaucratic oddity that prattles on in a maze of buildings at its headquarters in Brussels, Belgium. Its members still bicker over a constitution, and although it has many lofty treaties, the EU is often powerless to force countries to follow its mandates, such as getting the Germans to ease up on the gas.

Yet the organization is at the diplomatic center of the continent’s most pressing issues: absorbing former Soviet bloc nations, widening trade with Asia, forming defense and energy policies, trimming the welfare state, integrating a growing Muslim population, improving relations with Washington after years of divisiveness and keeping Russia, with its dominance of oil and gas markets, as an economic partner.

The EU doesn’t have its own army and historically hasn’t been regarded as a major international player. Its overall economy has been sluggish for years, and it has failed to fulfill many of its promises, such as becoming a leader in technology and knowledge-based economies.

But the bloc has become unified and active on issues including global warming and peace in the Middle East. Some European officials believe that even though the EU isn’t a global power, it has the duty to act like one, especially as the complement and counterbalance to American policy.

“The EU has to orient itself to the outside world now,” Klaus Haensch, former president of the European Parliament, told German media recently. “Someone who is an economic giant but wants to stay a political dwarf is not acting modestly, but irresponsibly.”

There is also the riddle of what exactly it means to be European, and how that elusive definition has further changed with the EU’s eastward expansion. Critics say Western members are not sensitive to countries such as Poland, which is more religious than increasingly secular France and Germany. Suspicion is also high over struggling democracies such as Bulgaria and Romania and the prospect that thousands of economic migrants will overrun Western capitals.

“I think there’s less of a willingness on the part of Western countries to share their wealth with the new members. This is a major problem,” said Ulrich Preuss, a public law and politics professor at Free University in Berlin. “There’s a feeling of overstretch that has emerged. And there’s a kind of alienation because Europe over the last 50 years has been Western Europe.”

When the leaders of member states gather in Berlin on Sunday for sausages, beer and yet another EU proclamation, German Chancellor Angela Merkel is expected to urge passage of a constitution by 2009. The lack of one reveals how some countries don’t fit comfortably under the European umbrella, especially voters in France and the Netherlands who rejected a draft constitution in 2005. Other nations, such as Britain, joined the EU but did not give up their native currencies.

In 1957, the signers of the Treaty of Rome that established the European Economic Community, a precursor to the EU, probably had little notion what their desire for an “ever closer union” would produce. Those countries – France, West Germany, Italy, Belgium, the Netherlands and Luxembourg – sought economic cooperation as a way to prevent future wars.