BERLIN — President Biden on Thursday strengthened his warning to Russia about a potential attack on Ukraine, saying that any movement of Russian units across the Ukrainian border would be taken as an invasion, a day after the president triggered alarm in European capitals with his suggestion of divisions among allies.
Mr. Biden, speaking to reporters at the White House after hours of efforts by his administration to walk back his comments in a news conference Wednesday, insisted that he had been “absolutely clear” with President Vladimir V. Putin of Russia that a new incursion in Ukraine would be met by a “severe and coordinated economic response.”
Mr. Biden retraced his rhetorical steps as Secretary of State Antony J. Blinken met with U.S. allies in Germany ahead of a critical Friday sit-down in Geneva with Foreign Minister Sergey V. Lavrov of Russia, after several rounds of inconclusive discussions over the huge buildup of Russian troops along Ukraine’s eastern border.
In his news conference on Wednesday, Mr. Biden said that a “minor incursion” by Russia into Ukraine could mean “we end up having a fight” with European allies about the appropriate response.
Although European diplomats said Mr. Biden had been merely stating the obvious, European capitals, including Kyiv, were unsettled by his earlier admission that the precise nature of Mr. Putin’s actions would determine “to what extent we’re going to be able to get total unity” among NATO allies.
It has also raised concerns that public signs of division between the United States and Europe — a goal in itself of Mr. Putin, analysts say — could embolden the Russian leader to mount a limited but still highly damaging attack on Ukraine.
In public, top European and NATO officials were quick to play down questions of division.
Speaking on CNN, NATO Secretary General Jens Stoltenberg rejected the idea that Mr. Biden had given Mr. Putin a green light to invade Ukraine with less than his full assembled force.
“Not at all, because the United States has been very clear over a long period of time,” Mr. Stoltenberg said. Appearing alongside Mr. Blinken in Berlin, Germany’s foreign minister, Annalena Baerbock, said that Europe had an “unequivocal unanimous commitment” to punishing Russian aggression against Ukraine.
But the European view has always been divided about what to do and in what circumstances to do it. As one senior European official said, the punishment must fit the crime. He noted that even after Russia had annexed Crimea, it took nearly a year for the European Union to respond with serious sanctions against Moscow.
In the current Ukraine crisis, the leaders of Germany’s new governing coalition have stopped short of a commitment to halt the $11 billion Nord Stream 2 natural gas pipeline, a joint Russian-German project that U.S. officials fear will enrich Mr. Putin and give him further leverage over European energy supplies.
And on Wednesday, President Emmanuel Macron of France surprised and irritated many European Union colleagues with an address to the E.U. Parliament in Strasbourg in which he called on Europeans to come up with their own proposal on European security. “We must build it between Europeans, then share it with our allies within the framework of NATO,” he said. “And then propose it for negotiation to Russia.”
French officials said Thursday that Mr. Macron was not seeking to undermine NATO’s unity. But the net effect of the words by Mr. Biden and Mr. Macron accentuated the frictions within the Western alliance, analysts said, a potential advantage for Russia.
“Biden’s comments coinciding with Macron’s speech looks uncoordinated, and given all the effort U.S. officials have spent traveling around Europe to keep people solid, it seems odd and didn’t need saying,” said Robin Niblett, director of Chatham House, a London-based research organization. “Musings about gradations of response opened up the can to put question marks back into the allied part of the debate.’’
Mr. Biden was asked on Wednesday whether the United States and its European allies could agree on what sanctions to impose on Russia should it further assault Ukraine, where it has supported a separatist war for nearly seven years.
Europeans and NATO are united with the United States in opposing any further Russian incursion into Ukraine, in pledging support of varying kinds for Ukraine, and in promising “massive costs” to Russia. But neither the United States nor Europe have detailed the exact steps they intend to take.
American and European officials have said that it was vital not to give Mr. Putin ammunition by public discussion of red lines. But Mr. Biden’s comments hinted at disagreements happening behind the scenes.
“It’s very important that we keep everyone in NATO on the same page,” Mr. Biden responded. “That’s what I’m spending a lot of time doing. There are differences. There are differences in NATO as to what countries are willing to do, depending on what happened, the degree to which they’re able to go.”
Ukrainian officials, among others, expressed dismay after Mr. Biden’s comments on Wednesday. “We want to remind the great powers that there are no minor incursions,” the Ukrainian president, Volodymyr Zelensky, wrote on Twitter on Thursday.
During a Thursday stop in Berlin, en route to a Friday meeting in Geneva with Russia’s foreign minister, Mr. Blinken added his voice to the cleanup effort.
Mr. Blinken said that “if any Russian military forces move across the Ukrainian border” in an act of aggression, the United States and its allies would deliver “a swift, severe and united response.”
Mr. Blinken’s words closely echoed a Thursday statement from the White House press secretary seeking to clarify Mr. Biden’s remarks. But he acknowledged the complexity of a situation in which Russia might assault Ukraine unconventionally, saying that the United States and its allies are “looking at every possible scenario” under which Russia could attack or destabilize Ukraine, to ensure “that we effectively define our coordinated response.”
Conceding “different authorities in our different countries” that could shape what nations take what steps against Russia, he insisted that “all of our countries have been clear about the massive consequences that Russia would face for renewed aggression.”
On that front, the Biden administration announced on Thursday that it would impose sanctions on four people it accuses of engaging in “influence activities” on behalf of Russia to destabilize Ukraine in advance of a potential invasion.
Understand the Escalating Tensions Over Ukraine
While in Berlin, Mr. Blinken conducted a flurry of diplomacy on the eve of his high-stakes meeting with his Russian counterpart, Mr. Lavrov, which could help determine whether a diplomatic solution to the crisis induced by Mr. Putin’s army can be achieved. Mr. Blinken met with Germany’s foreign minister and its new chancellor, Olaf Scholz, and with diplomats from Germany, France and Britain who gathered under the moniker of the Transatlantic Quad.
He later delivered a speech at the Berlin-Brandenburg Academy of Sciences outlining the stakes of the Western showdown with Moscow over Ukraine, arguing that “it is a crisis with global consequences” for the international system of established borders and state sovereignty.
“Perhaps no place in the world experienced the divisions of the Cold War more than this city,” Mr. Blinken said. “It seems at times that President Putin wants to return to that era.”
But it was clear that Mr. Biden’s news conference had ruffled the alliance.
Ulrich Speck of the German Marshall Fund in Berlin said that Mr. Biden was using the kind of language allies speak to one another. “But that’s not the way you talk to the Russians, because when you talk to the press you talk to the Russians,” he said. “If the point is to reinforce allied unity, this was an unforced error.”
The European Union considers that its main strength is in economic sanctions, and those are an active subject of intense and secret discussions, senior European officials say. Tough sanctions will come if Russia does not respond to diplomacy, but inevitably they will be calibrated to what Russia actually does.
In its new action on Thursday, the Biden administration said that it would impose sanctions on four people. Two of them, Taras Kozak and Oleh Voloshyn, Ukrainian parliamentarians, have used their influence to undermine Ukraine’s leadership in coordination of Russia’s security agency, the Biden administration said. The others, Volodymyr Oliynyk and Vladimir Sivkovich, are former Ukrainian officials who worked with Russian intelligence agents to build support for Ukraine to cede Crimea to Russia.
It has been broadly agreed within the alliance that the costs of a new Russian incursion would be punishing and severe, but some countries are more wary than others, and all know that such measures will hurt the European economy far more than the American one. That is especially true given high energy prices and that Europe still gets 40 percent of its natural gas and 25 percent of its oil from Russia.
Mr. Blinken’s visit to Germany also came amid reports that the U.S. had authorized the Baltic nations of Latvia, Lithuania and Estonia to transfer American arms to Ukraine, including anti-armor missiles and other U.S.-made weapons. A Congressional aide confirmed the reports, and a State Department spokesman did not deny them.
French officials emphasized on Thursday that Mr. Macron had said that Europeans should talk among themselves, then talk to NATO before talking to Russia. They argued that he was only trying to further his campaign for Europe to develop “strategic autonomy.”
After Mr. Macron’s speech, Europe’s top foreign policy official, Josep Borrell Fontelles, spoke to both Mr. Blinken and Mr. Stoltenberg and agreed on what he called the need for “a strong, clear and united trans-Atlantic front.” The European Union has agreed “to further strengthen coordination with the United States and with NATO,” Mr. Borrell said, and he invited Mr. Blinken to attend a meeting of E.U. foreign ministers on Monday to discuss the Ukraine crisis.
Mr. Stoltenberg then said in a separate statement that the call was a “strong signal of unity,” repeating Mr. Blinken’s plea on Wednesday to avoid “divisions between and within our countries.”
Michael Crowley reported from Berlin, and Steven Erlanger from Brussels. Alan Rappeport contributed reporting from Washington.