LONDON – On New Year’s Day almost a decade ago, cash registers and ATMs across Europe started spitting out the shiny coins and crisp notes of the world’s newest currency, the euro.

They were the most radical, tangible symbol of the long march toward reconciliation and harmony on a continent still haunted by the memories of two world wars. A single currency, proponents said, would seal an era of European unity that already boasted free markets and free movement.

Now, officials are working feverishly to ensure that the currency survives a raging debt crisis that threatens its 10th birthday. And like a mantra, many repeat the stark warning issued by German Chancellor Angela Merkel: “If the euro fails, Europe fails.”

But would it?

Not if you ask Constanze Stelzenmueller. A resident of Berlin, she knows plenty of people from one European country who happily study, work and live in another. She enjoys the ease of travel around the continent without a passport. And as a lawyer, she is aware that a mass of laws and regulations now bind the region’s nations together tightly, with or without a shared currency.

“It’s impossible to turn the clock backward on the European Union,” said Stelzenmueller, an analyst with the German Marshall Fund. “We are a big tissue of integration which is not going to fall apart even if the euro does.”

All eyes are now trained on the expected conclusion today of a summit in Brussels that many believe could prove pivotal in the history of both the euro and the EU, whose roots go back six decades. Leaders of the 27 member states, 17 of which use the common currency, are to thrash out an agreement proposed by France and Germany that would see at least a majority of them signing up to a closer fiscal and economic union, with strict limits on government spending and borrowing to prevent future debt crises.

The two-day meeting has been described by some analysts and even one top EU official as a last-chance saloon. Without a pact, they say, on fiscal integration and aggressive action by the European Central Bank to shore up debt-racked countries such as Spain and Italy, the euro risks being trampled to death by bolting investors.

But such dire prognostications were also issued before a similar so-called make-or-break summit in October that turned out to be a disappointment.

German officials are already suggesting that a deal on establishing a fiscal union could take a few more weeks to complete. The negotiations are sensitive because of the significant loss of sovereignty implied by the pact, which would require countries to submit their national budgets for review by a higher European authority.

There is some resistance to the idea of Europe being remade in Germany’s image through the emphasis on fiscal rigor. Also, smaller EU members are loath to be bossed around by the Paris-Berlin axis. And the 10 countries that do not use the euro, Britain chief among them, worry that an agreement limited to the 17 eurozone nations would create a two-tier EU, shutting them out of important future decisions on economic policy.

Hope that the debt crisis would be definitively faced down this week was set back Thursday when Mario Draghi, the new head of the European Central Bank, said he had no plans to step up purchases of bonds of distressed nations. The markets had expected Draghi to unleash more of the ECB’s firepower after he hinted last week that a fiscal compact by the EU would prompt him to do so.

“Time is working against us,” French President Nicolas Sarkozy warned in a speech in southern France on Thursday. “Never has the risk of Europe blowing apart been so great.”

Yet even if the euro were to implode, it is far from certain that it would spell the end of the dream of European unity, as Merkel and others claim.

“Europe doesn’t fail if the euro fails,” said Giles Merritt of Friends of Europe, a Brussels-based think tank. “It would certainly be deeply humiliated, in chaos, and facing a very major crisis.”

At the same time, Merritt noted, “the great bulk of European public opinion knows that, for all its imperfections, an integrated Europe is the answer” in an age of rising powers elsewhere, such as in Asia.