Until very recently, the U.S. view of the European Union has focused on rolling currency crises and rollbacks in NATO readiness. But in Ukraine, the view was quite different. Compared with the corrupt, incompetent governance of President Viktor Yanukovych, the European Union was perceived by many Ukrainians to be a democratic and economic model to emulate and join. In fact, recent events in Ukraine — mass protests in Kiev, Yanukovych being deposed, Russia’s incursion into Crimea — were triggered when Yanukovych backed out of an E.U. association agreement.

The U.S. view of the E.U. may be about to change, too, assuming it coalesces around a muscular diplomatic and economic response to Russia’s territorial aggression. While there may not be a viable military response, Ukraine must be prevented from slipping into an economic and political abyss, and Russian President Vladimir Putin needs to be pressured to recalculate the cost-benefit analysis of illegally annexing Crimea. These objectives are best served by developing and implementing a coordinated Western response.

While no action is yet final, indications are that the E.U. is rising to the challenge. This is significant given the fractious nature of the 28-nation union and the economic risks that could come from punishing Russia. These risks are higher in Europe than in the United States, because many E.U. countries are economically intertwined with Russia and deeply dependent on Russian energy exports.

E.U. members reportedly are coordinating the severity and timing of sanctions. It’s likely the response will wait until after Sunday’s bogus referendum in Crimea, which Russia may use as a political fig leaf for annexation.

As important, the E.U. may cut tariffs on goods exported from Ukraine, giving the country the benefits of the deal Yanukovych rejected after Putin pressured him to join a rival Russian-led Eurasian Customs Union.

The E.U. recognizes the gravity of what’s unfolding in Ukraine, João Vale de Almeida, the union’s ambassador to the United States, said in Minneapolis on Monday. Speaking at a Minnesota Trade Office event at the Dorsey & Whitney law firm, Vale de Almeida called the situation “the most serious crisis since the end of the Cold War in the European theater” and said the E.U. condemns and does not accept the violation of Ukraine’s territorial integrity. While calling for diplomacy to defuse the crisis, he emphasized that despite the potential economic damage to many of Europe’s sclerotic economies, what the E.U. has in common with the United States — “good old values of democracy, freedom, human rights and rule of law” — would prevail.

“Europe will not sacrifice values to economic arguments,” he said, adding that there are two sides to dependence: Russia’s gas- and oil-oriented economy could take a hard hit, too.

The crisis is crucial for Crimea and Ukraine. But it also threatens Europe and the entire international order. Consider just one possible ramification: nuclear weapons proliferation, one of the gravest global threats.

North Korea has used the nuclear threat to menace Asian neighbors. And six world powers central to current diplomatic efforts on Crimea — including Russia, the United States, France, Germany and the United Kingdom — are negotiating with Iran over its potential nuclear weapons program. If Iran develops a nuclear weapon, the volatile Mideast could be on the verge of a nuclear arms race.

In the wake of the breakup of the Soviet Union, Ukraine — then the third-largest nuclear nation — relinquished its arsenal predicated on a treaty that guaranteed its territorial sovereignty. Russia sends a devastatingly dangerous signal to all nations considering proliferation if it refutes a nuclear weapons treaty it is party to.

Other international issues, like Syria, could also be impacted if diplomacy fails and Russia annexes Crimea. If Russia does not defuse the crisis, it must be held to account, and European and American solidarity is essential in responding to the crisis.