The Biden administration has briefed European allies in recent days about the potential for a new Russian military operation in Ukraine as Moscow continues to mass troops along the contested border in the latest escalation of tensions between the two neighbors, U.S. and European officials said.

In briefings with North Atlantic Treaty Organization counterparts as well as individually with a number of European Union allies, U.S. officials shared concerns that Russia might try to take offensive action in the near future, the...

The Biden administration has briefed European allies in recent days about the potential for a new Russian military operation in Ukraine as Moscow continues to mass troops along the contested border in the latest escalation of tensions between the two neighbors, U.S. and European officials said.

In briefings with North Atlantic Treaty Organization counterparts as well as individually with a number of European Union allies, U.S. officials shared concerns that Russia might try to take offensive action in the near future, the officials said.

The briefings, based on U.S. intelligence assessments, were aimed partly at trying to get European allies to appeal to Russia to help de-escalate tensions, the officials said.

The officials declined to give details of any evidence that the U.S. shared, but said there was no clear information pointing to a Russian attack, despite an increased Russian military presence recently at the border and an increase in cease-fire violations in eastern Ukraine.

European capitals are watching the situation closely, the officials said. “I don’t think the evidence is really that clear in either direction,” said one European official. In Washington, Pentagon officials met Friday to discuss the issue and are watching developments intently, a U.S. official said.

Richard Moore, at The Wall Street Journal's CEO Council Summit, says Russia's behavior around Ukraine in recent weeks is destabilizing. (May 2021) Photo: Foreign and Commonwealth Office/Reuters The Wall Street Journal Interactive Edition

Ukrainian officials said the situation appeared less menacing and farther from the border than in April, when Russia amassed thousands of troops around its neighbor’s territory. Russia claims Ukraine, a former Soviet republic, as part of its sphere of influence. Ukraine is seeking deeper integration with NATO and the EU.

The Kremlin said that troop movements on its own territory were Russia’s business alone, and that it would take national-security measures as it saw fit in response to NATO’s military moves.

“Russia does not pose a threat to anyone,” Kremlin spokesman Dmitry Peskov told reporters. Bloomberg reported on the U.S. briefings on Thursday.

The White House said there have been “extensive interactions” with European allies, including Ukraine, regarding reports of the Russian military buildup at the border with Ukraine.

“As we’ve made clear in the past, and we’ve made clear directly to them as well, escalatory or aggressive actions by Russia would be of great concern to the United States,” White House press secretary Jen Psaki

told reporters Friday. “Obviously, our European conversations are about shared concern” regarding the Russian actions.

Berlin and Paris in recent days have pressed the Kremlin to return to international talks to resolve the conflict in eastern Ukraine.

On Friday, France’s Foreign and Defense Ministers, Jean-Yves Le Drian and Florence Parly, issued a blunt statement after meeting their Russian counterparts, Sergei Lavrov and Sergei Shoigu, in Paris.

“The two ministers expressed their concerns about the deteriorating security situation in Ukraine and clearly warned of the serious consequences of any further possible damage to the territorial integrity of Ukraine,” the statement by the French officials said.

They called on Moscow to adhere to its commitments to remain transparent about its military movements and activities.

Russia seized Crimea from Ukraine in 2014 and fomented a conflict in eastern Ukraine, sending troops covertly across the border to carve out two self-declared separatist statelets. Large-scale fighting ended in 2015, but cease-fires have been unstable and shooting continues across largely fixed front lines, adding to the around 14,000 deaths in the conflict.

Mason Clark, a Russia analyst at the Institute for the Study of War in Washington, a nonpartisan research organization, said experts haven’t seen a new overt Russian buildup in recent weeks. But, he said, a shuffling of units that arrived in the region earlier this year could spell trouble.

Mr. Clark said Moscow’s decision to keep the troops in the vicinity of Ukraine and Belarus, rather than return them to their home base in Siberia, could mean plans for an offensive. But, he added, it also could signal what the Kremlin sees as new geopolitical realities--namely that with worsening relations with the West, any Cold War-style front line lies near Ukraine and Belarus.

“We still do not see an imminent attack on Ukraine,” he said. “But we do see many things are in place that could make it a possibility.”

—Alan Cullison contributed to this article.

Write to James Marson at james.marson@wsj.com, Vivian Salama at vivian.salama@wsj.com and Laurence Norman at laurence.norman@wsj.com