ATHENS  “The Italians, the Spaniards, the Greeks, we all have been living in happy land, spending what we did not have,” said George Economou, a Greek shipping magnate, contemplating his country’s economic troubles and others’ from his spacious boardroom. “It was a fantasy world.”

For some of the countries on the periphery of the 16-member euro currency zone  Greece, Ireland, Italy, Portugal and Spain  this debt-fired dream of endless consumption has turned into the rudest of nightmares, raising the risk that a euro country may be forced to declare bankruptcy or abandon the currency.

The prospect, however unlikely, is a humbling one. The adoption of the euro just a decade ago was meant to pull Europe together economically and politically, ending the sometimes furious battles over who could devalue their currency the fastest and beggar their neighbor.

For the Continent, the currency signaled the potential to one day rival the United States. For its poorer countries, winning admission to the euro zone was a point of pride, showing that they had tamed their budget deficits and set their financial houses in order.