Macron meets Putin in Moscow, aiming for a de-escalation.

President Emmanuel Macron of France, who has positioned himself at the center of Europe’s furious diplomatic maneuvering over Ukraine, said on Monday that the continent was at a “critical crossroads” as he met in Moscow with President Vladimir V. Putin of Russia.

Amid fears over Russia’s military buildup surrounding Ukraine, Mr. Putin and Mr. Macron met at the Kremlin, sitting some 20 feet apart at a long table to maintain social distancing. In televised opening remarks, the Russian president spoke to his French counterpart using the informal form of address, and praised France for trying to resolve the “fundamental questions of European security.”

Mr. Macron said that he hoped the meeting would begin a process of de-escalation, adding: “This dialogue is absolutely essential, more than ever, to ensure the security and stability of the European continent.”

Later, President Biden was scheduled to hold his first meeting with Germany’s new chancellor, Olaf Scholz, in the hope of strengthening Western nations’ response to Russia. Mr. Putin is demanding a rollback of NATO’s presence in Eastern Europe, and has massed troops near Ukraine’s borders — about 130,000 according to U.S. and Ukrainian officials, in what they say appears to be preparation for a full-scale military assault.

With the Biden administration staking out a hard line against Moscow, Germany so far lying low and Mr. Putin seemingly determined to force a solution to Russia’s security grievances, Mr. Macron has emerged as a key player in Europe’s attempts to ease one of the continent’s gravest security crises since the end of the Cold War. He was scheduled to continue his diplomatic outreach on Tuesday with a visit to Ukraine and a meeting with President Volodymyr Zelensky in Kyiv.

Mr. Macron has urged a more conciliatory approach toward Mr. Putin than the United States and Britain have taken, and the two presidents have spoken several times recently by phone.

On Monday, Mr. Putin’s spokesman, Dmitri S. Peskov, said the Kremlin expected “a very substantive and lengthy conversation” during a meeting and working dinner, which would be followed by a joint news conference.

“Of course, the situation is too complicated to expect some breakthroughs as a result of just one meeting,” Mr. Peskov said. “But we know, and Macron told Putin that he will bring some ideas that could help de-escalate tensions, and that he plans to share these ideas.”

French officials said that in his meetings with Mr. Putin and Mr. Zelensky, Mr. Macron would seek to use the Normandy Format — a grouping of France, Germany, Ukraine and Russia — to bolster the 2015 Minsk 2 agreement that secured a cease-fire between Ukrainian forces and Russia-backed separatists in eastern Ukraine.

In an interview published on Sunday in the Journal du Dimanche, a French newspaper, Mr. Macron said that he did not believe Russia’s goal was to seize Ukraine, but to “clarify the rules of cohabitation” with NATO and the European Union. Russia has called for Western countries to scale back their presence in Eastern Europe to mid-1990s levels. Mr. Macron said that Russia had a right to seek security guarantees, while emphasizing that “efficient and lasting dialogue” with Russia would not lead to the “weakening” of regional states that fear Russian aggression.

On Monday, Mr. Macron tweeted: “Let us start building a response that is useful for Russia, useful for all of our Europe, a response that helps us avoid war and build all the elements of trust, of stability, of visibility. Together.”

His stance has sometimes been in contrast to that of the United States, which has rejected Mr. Putin’s main security demands outright. Last week, Mr. Biden ordered the deployment of 3,000 additional U.S. troops to help secure NATO allies in Eastern Europe, although he has emphasized that he will not send forces to Ukraine.

Russia has denied plans to invade Ukraine, and accused the United States of instigating tensions. On Monday, Maria Zakharova, a spokeswoman for Russia’s foreign ministry, said that Washington and its British allies were demonizing Moscow in order “to divert public attention from domestic political crises, invest billions of dollars into arming ‘fragile democracies’ and use the situation to reinforce their ‘invincible’ image, which has been frayed by the debacle in Afghanistan.”