German Chancellor Angela Merkel talks with leaders of other European nations after a group photo on the first day of their two-day summit in Brussels. (Jack Taylor/Getty Images)

Furious over Russia’s bombardment of Aleppo, European leaders warned the Kremlin on Thursday that it could face consequences if it maintains its offensive against the besieged rebel-held part of the Syrian city, although they fell short of the unity required to impose new sanctions.

The sharp rhetoric was a substantial departure for European leaders, who have long been focused on when they can dial back existing sanctions on Russia, not ramp them up. Instead, Russian actions in recent weeks have upended the conversation. From the Russian-backed pummeling of Aleppo to the shipment of nuclear-capable missiles to ­Kaliningrad, the recent steps have galvanized Western anger and plunged relations to fresh depths. The warnings came as leaders gathered in Brussels for a summit in part to discuss relations with Russia.

Europe’s toughened stance marks a partial victory for Washington, which has struggled to maintain European unity on sanctions and has long taken a harder position on Russia than its partners across the Atlantic. The stand also reflects the toll of Russia’s actions in Syria, where it has partnered with the regime of President Bashar al-Assad in a punishing campaign that has made little distinction between combatant and civilian.

“The bombardment of Aleppo is a disregard of principles of humanity, and we cannot accept it,” German Chancellor Angela Merkel said after leaders discussed Russia over dinner. “We will have to envisage any conceivable measure in order to respond.”

A day earlier, she and French President François Hollande met with Russian President Vladimir Putin in Berlin to discuss Ukraine and Syria. Both she and Hollande blasted Russian actions in Syria and said they would push for a stiff European response. They have called for a full cease-fire in Syria along with an end to the offensive on Aleppo.

A worker arranges cheese at a grocery store in St. Petersburg. European leaders warned the Kremlin that it could face new sanctions if it maintains its offensive against Aleppo. (Alexander Demianchuk/Reuters)

Russia said earlier this week that it would temporarily halt airstrikes on Thursday. While the European leaders were meeting Thursday, Russian Defense Minister Sergei Shoigu announced that the pause would be extended by a day.

That did little to assuage the European anger.

“The ambition of turning Aleppo into a new Grozny, this is absolutely unacceptable,” said Estonian Prime Minister Taavi Roivas as he arrived at the summit. Russian forces used scorched-earth tactics against the Chechen capital of Grozny in a bitter domestic offensive early in Putin’s tenure.

But after an hours-long discussion, leaders held back from a formal threat to issue new sanctions against Russia related to Syria, a sign that there is no unanimity among Europe’s 28 members on the subject.  E.U. diplomats said that could change if outrage in­creases over Russia’s conduct. Current sanctions related to Ukraine are set to expire in December, but there is little question now that they will be extended.

“We could have been looking forward to a different discussion if it weren’t for what is happening in Syria,” a senior E.U. diplomat said, speaking on the condition of anonymity to assess the closed-door talks. “The Russians, rather than de-escalating the situation, are sadly escalating it.”

Some E.U. nations, including Italy, Spain and Hungary, have favored ending the sanctions. Last month, Vice President Biden said that “at least five countries right now . . . ‘want out’ ” of the sanctions tied to Ukraine, without specifying which countries he was referring to.

But in the intervening weeks, the situation has changed significantly. Italian Prime Minister Matteo Renzi, who called for the discussion about Russia, was just feted at a White House state dinner and has dialed back his efforts to find new ways to engage with Russia. He still led opposition to new sanctions, diplomats said. Hollande called off a planned visit to Paris by Putin and, after months of appearing eager to scale back sanctions, has recast himself as a hawk on Russia.

“We have to put all the pressure necessary for the truce to be extended,” Hollande said as he arrived at the summit. 

That meant that the dinnertime talk on Russia turned into a discussion of what further measures might be possible. Several leaders outlined their assessments of how the Kremlin was interfering with their political systems by targeting their media markets with disinformation and fueling far-right, Euroskeptic parties with money and logistical support.

The discussion echoed one in the United States, where intelligence agencies blame Russia for hacking the computer systems of Democratic officials in an apparent bid to influence the presidential election.