“The battle being threatened cannot be underestimated in its violence,” Mr. Nehammer said in a news conference after the 75-minute meeting at Mr. Putin’s residence outside Moscow that the visitor described as blunt and direct.

The Austrian chancellor said he had told the Russian president that as long as people were dying in Ukraine, “the sanctions against Russia will stay in place and will be toughened further.”

The Kremlin, playing down the meeting’s significance in a terse statement, said only that it was “not long by the standards of recent times.”

Even as Mr. Nehammer was visiting, Russian forces were bombarding Ukrainian cities and towns, and President Volodymyr Zelensky of Ukraine said “tens of thousands are dead” in Mariupol, the besieged southern city that has been the scene of the most intense destruction of the war.

And Mr. Putin, despite Russia’s military blunders in the war, and for all the Western efforts to ostracize him, still appeared in control of the crisis. He has severely repressed any dissent and benefited from widespread domestic support, continuing revenues from oil and gas sales to Europe, the implicit backing of China and the refusal of much of the world to join sanctions against Russia.

Many commentators in the West had criticized the Austrian chancellor — his country is a member of the European Union but not of NATO — for having visited Moscow at all, seemingly playing into Mr. Putin’s narrative that American-led efforts to isolate Russia would necessarily end in failure.

Mr. Nehammer told reporters afterward that he had tried to confront Mr. Putin with the horrors of war and of the war crimes that Russian troops are accused of having committed in the Kyiv suburb of Bucha and elsewhere. He said he also had told Mr. Putin about the destroyed Russian tanks he saw on a recent visit to Ukraine, to make clear the enormous loss of life that Russia was suffering.

Mr. Nehammer said that Mr. Putin had brushed aside the accusations of war crimes as having been staged by Ukraine.

At the end, Mr. Putin told him: “It would be better if it” — the war — “ended soon,” Mr. Nehammer said, but the meaning of those words was unclear, since they could either signal that Mr. Putin was prepared for further peace talks or that he could be readying a quick and brutal assault in the Donbas, where Russian-backed separatists have been fighting Ukraine’s military since 2014.

“We can have no illusions: President Putin has totally adopted the logic of war, and is acting accordingly,” Mr. Nehammer said. “This is why I believe it is so important to permanently confront him with the facts of the war.”

How much more brutal the war could become was signaled in an interview with Eduard Basurin, a separatist commander, aired on Russian state television. Mr. Basurin said that with Ukrainian forces ensconced in underground fortifications at a steel plant in Mariupol, storming the redoubt did not make sense. Instead, he said, Russian forces needed to first block the exits and then “turn to the chemical troops who will find a way to smoke the moles out of their holes.”

Mr. Putin was silent on Monday but was expected to speak publicly on Tuesday, when he will travel to the Vostochny spaceport in Russia’s far east with President Aleksandr G. Lukashenko of Belarus, his ally, to mark the annual Cosmonauts’ Day.

The Feb. 24 invasion of Ukraine has increasingly been framed by Mr. Putin as not against that country, but against the West — specifically, the United States, as the supposed patron of Mr. Zelensky’s government and its aspirations to escape Russia’s sphere of influence as a former Soviet republic.

Sergey V. Lavrov, Russia’s foreign minister, said in a Russian television interview that aired on Monday that what the Kremlin calls its “special operation” in Ukraine is aimed at rolling back American influence — which the Russian government characterizes as the root of the world’s ills.

“Our special military operation is designed to put an end to the reckless expansion, and the reckless course toward complete dominance, of the United States,” Mr. Lavrov said.

The United States and European Union have imposed increasingly severe economic sanctions on Russia over the invasion and are sending weapons to Ukraine’s military. But they do not want to get drawn into a war with Russia. And the European Union remains reluctant to ban Russian oil and natural gas, which remain critical to the bloc’s own economic health.

E.U. foreign ministers met on Monday in Luxembourg and the bloc’s foreign policy chief, Josep Borrell Fontelles, said that “nothing is off the table, including sanctions on oil and gas.”

While ministers discussed a possible phaseout of Russian oil, more easily replaceable from other suppliers than gas, the meeting also laid bare the bloc’s divisions. Austria, Hungary and Germany opposed any effort, for now, to restrict Russian gas imports.

Still, European Union leaders were expected to approve another 500 billion euros in funds to repay member states for sending weapons to Ukraine, which would mean a total of 1.5 billion euros so far — nearly equivalent to the $1.7 billion in weapons that the United States has authorized.

Russian troops, having retreated from northern Ukraine after a failed effort last month to reach the capital, Kyiv, have been resupplying and regrouping in Russia and Belarus so they can join the battle in eastern Ukraine. But Western officials said on Monday that effort may still take some time.

Ukrainian officials have been warning since last week that civilians in east Ukraine should flee while they can. Mr. Zelensky warned that tens of thousands of Russian troops were preparing a renewed assault there.

If and when the southern port city of Mariupol finally falls, Russian troops can move north to meet up with Russian troops attempting to move south from Izyum and try to encircle the bulk of Ukraine’s army, which is concentrated further east, said Mathieu Boulègue, an expert on the Russian military at Chatham House, the London research institution.

That is easier said than done, Mr. Boulègue said, as the battered Russian troops await reinforcements. The Ukrainians, he said, were trying to block the Russians and organize a counterattack that would be more complicated than the fighting around Kyiv, which had forced the Russians to retreat.

Given the reports of Russian atrocities at Bucha, Kramatorsk, Mariupol and other cities, negotiations between the Ukrainian and Russian governments are on hold.

But few believe that the antagonists are ready for real talks, because Mr. Putin needs to show more military gains and because the Ukrainians believe that they can still repel the Russians, said Ivo Daalder, former U.S. ambassador to NATO.

“The Ukrainians think they have an opportunity not just to prevent Russia from gaining more ground in the east but expelling them from there, while Putin needs to find something he can sell as a victory,” Mr. Daalder said. “So diplomacy is not going anywhere.”

If and when talks on a settlement finally occur, Mr. Putin will inevitably be part of them, said François Heisbourg, a French defense expert. Diplomats deal with leaders of governments, no matter how distasteful, he said.

The West also hopes that increasing economic pain will encourage Mr. Putin to scale down the war and end it. Russia is already is “deep recession” and its economy is expected to shrink by 11 percent this year, the World Bank reported.

But the impact is severe on Ukraine, too. The bank forecast that Ukraine’s economy would shrink by about 45 percent this year because of the Russian invasion and the impact of a “deep humanitarian crisis.”

Mr. Putin originally named one goal of the war as the “denazification” of Ukraine, falsely labeling as Nazis those who resist Russian domination. An article on Monday in a Russian state newspaper, Parlamentskaya Gazeta, written by an adviser to the chairman of Russia’s lower house of Parliament, expanded on that concept to define the enemy as “Ukrainian-American neo-Nazism.”

The fight also included a “cold war” against enemies of the state inside Russia, the article said, adding: “The denazification of Ukraine is impossible without a parallel denazification of Russia.”

It was the latest sign that, even as the war in Ukraine rages, Mr. Putin is priming his security apparatus for an ever-widening intolerance for dissent. The crackdown has accelerated in recent weeks, with pro-war Russians turning in teachers and neighbors who speak out against the war.

Last Friday, Russia closed some of the last remaining independent institutions of civil society, including the Carnegie Moscow Center and the Moscow offices of Human Rights Watch and Amnesty International. It expanded the practice of naming government critics as “foreign agents,” for the first time adding a popular musician to the list: the rapper Ivan Dryomin, 25, who goes by the name Face.

Steven Erlanger reported from Brussels and Anton Troianovski from Istanbul. Reporting was contributed by Monika Pronczuk in Brussels.