Before President-elect Donald Trump’s surprise victory last week, European leaders seemed certain to renew sanctions on Russia for its ongoing aggression against Ukraine. The sanctions are up for renewal at a meeting next month, and Moscow has done nothing to meet Western conditions. On the contrary, Russian military attacks in Aleppo, in which hundreds of Syrian civilians have been killed and a humanitarian convoy was attacked, have hardened European views toward Russia.

The Obama administration has worked closely with the European Union to ensure trans-Atlantic unity on sanctions, arguing that they are crucial to containing Russia. But Trump’s victory threatens this tenuous agreement by providing skeptical European nations with a credible argument against renewal: Trump will lift U.S. sanctions soon anyway. Thus, before even entering office, Trump may cause the sanctions regime to crumble, reducing pressure on Moscow and emboldening Putin.

Even before Trump’s victory, the sanctions already faced deep suspicion among certain European countries. Leaders in Italy, Hungary, Slovakia, Greece and Cyprus have argued that not only are sanctions not working but, combined with the drop in oil prices, they are hurting EU members economically. Any single one of those countries could upend the current sanctions regime because renewal requires agreement among all 28 EU member states.

Thanks to diligent work by U.S. and EU officials, that consensus has held so far, but it is likely to dissolve in light of Trump’s expressed intentions toward Moscow. Even among the staunchest supporters of sanctions — Germany, Poland, the U.K. and the Baltic states — maintaining such measures will become untenable if it looks like the United States will break ranks.

EU leaders clearly understand this risk. On Sunday, EU foreign policy chief Federica Mogherini said the EU has “a very principled position on the annexation of Crimea and the situation in Ukraine” that was not going to change “regardless of possible shifts in others’ policies.” Mogherini’s efforts are valiant, but the likelihood that Europe will roll over sanctions for another six months has plummeted. Why would Europeans want to lock in their sanctions against Russia when the incoming American leader and many of his campaign advisers have indicated a desire to lift U.S. sanctions against Russia and even recognize Russia’s illegal annexation of Crimea?

During the campaign, Trump repeatedly hoped for better relations between Russia and the United States. “Wouldn’t it be great if we got along with Russia?” he rhetorically asked on numerous occasions, voicing his desire to cooperate with Moscow to fight ISIS, even though most Russian strikes in Syria over the past year have been against non-ISIS targets.

Trump also repeatedly expressed admiration for Putin during the campaign and indicated an interest in meeting with the Russian leader before his inauguration next Jan. 20. In an interview last week with The Wall Street Journal after his victory, he voiced a desire to start the relationship with Putin, whom he has never met, with a phone call. On Monday, the two spoke and agreed on the need to improve relations. Trump has extolled the Russian president for his strong leadership. Speaking in New York last Thursday, Putin’s spokesman Dmitri Peskov said Trump and the Russian president hold “the same foreign-policy principles.” We sure hope that is not the case.

Controversy about ties to Russia shadowed Trump throughout the campaign. At a real estate conference in 2008, Trump’s son Donald Jr. reportedly declared, “Russians make up a pretty disproportionate cross-section of a lot of our assets. We see a lot of money pouring in from Russia.”

There are also concerns about several of his advisers. Retired Lt. Gen. Michael Flynn, who many speculate will be national security adviser in the next administration, appeared at the 10th anniversary dinner last December for RT, one of the Kremlin’s most scurrilous propaganda outlets. Flynn sat at Putin’s table and was reportedly paid to give a speech during the festivities. Although Flynn’s defenders claim he was tough on Putin in conversation, no independent evidence has emerged to confirm that. Paul Manafort served as Trump’s campaign chairman until controversy over his ties in Ukraine to the pro-Russian former President Viktor Yanukovych forced him off the team in August. Carter Page, cited by Trump as an adviser earlier this year, has had various business dealings in Russia and gave a speech in Moscow in July in which he slammed U.S. policy toward Russia.

All of these individuals have called for lifting sanctions on Russia and returning to a normal bilateral relationship. Another close Trump adviser and potential secretary of state, former House Speaker Newt Gingrich, alarmed Estonia, a NATO member state that enjoys Article 5 guarantees for common defense, by dismissing it as a “suburb of St. Petersburg,” located in Russia.

Of course, as Trump gets briefed he may well reconsider some of these positions and send some stronger signals to both Europe and Russia about the need for continuity of the sanctions — at the very least until he and his team are in place. President Barack Obama suggested after their Oval Office meeting that Trump intended to maintain U.S. commitments to European allies, a hopeful sign, and some of the names under consideration for Cabinet positions seem to share the more-tough minded views expressed by Vice President-elect Mike Pence in his vice presidential debate with Sen. Tim Kaine. If that proves to be the case, no one would be happier than we to have our concerns allayed.

Before Nov. 8, nobody in Europe believed Trump would be the next U.S. president. Now, even before he takes the oath of office, Trump could upend EU policy toward Russia and derail the sanctions regime. Lifting Western sanctions on Russia while it still occupies Ukrainian territory would embolden Putin into thinking he has reconsolidated a sphere of influence along his borders. It would put an end to the effort to impose costs for his military aggression without requiring him to live up to any of the conditions, including withdrawal of forces and return of control of the border to Ukraine, required by the Minsk cease-fire agreement signed in February 2015.

It would abandon Ukraine in its time of need and betray other countries formerly part of the Soviet Union that aspire for closer ties with the West. It also would mark a return to “Big Power” politics at the expense of smaller countries in the region and principles of sovereignty and territorial integrity, calling into question the post-Cold War dispensation of a Europe “whole and free.”

Without U.S. leadership keeping the Europeans united against Putin, Western resolve in the face of Russian aggression will crumble. Before even moving to 1600 Pennsylvania Ave. and gaining the authority to lift U.S. sanctions on Russia, Trump could produce a radical change in policy toward Moscow.

Such a change, however, would not make America, the West or the world great again. But it could trigger the unraveling of the alliances and institutional structures that made the U.S. and its European partners great in the past.

Eric Edelman is former undersecretary of defense for policy (2005-09). David J. Kramer served as assistant secretary of state for democracy, human rights and labor at the end of the George W. Bush administration.

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