President Vladimir V. Putin of Russia addressed a rally and concert in Red Square on Friday celebrating Russia’s illegal annexation of four Ukrainian provinces.Credit…Alexander Nemenov/Agence France-Presse — Getty Images

President Vladimir V. Putin asserted on Friday that Russia would annex four Ukrainian regions and decried the United States for “Satanism,” in a speech that marked an escalation in Moscow’s war against Ukraine. In starkly confrontational terms, he positioned Russia as fighting an existential battle with Western elites he deemed “the enemy.”

Speaking to hundreds of Russian lawmakers and governors in a grand Kremlin hall, Mr. Putin said that the residents of the four regions — which are still partially controlled by Ukrainian forces — would become Russia’s citizens “forever.” He then held a signing ceremony with the Russian-installed heads of those regions to start the official annexation process, before clasping hands with them and chanting “Russia! Russia!”

The Biden administration quickly condemned the annexations, saying they “have no legitimacy,” and enacted a round of new sanctions on Russia’s defense and technology industries as punishment for Moscow’s actions.

Mr. Putin’s address came against a backdrop of Russian setbacks on the battlefield, where Ukraine’s forces have scored stunning victories in recent weeks in the east. As the Russian leader spoke, Ukrainian officials said their army had moved closer to encircling the Russian-occupied town of Lyman, a strategically important hub in the Donetsk region that lies inside the territory Mr. Putin is claiming.

Even by Mr. Putin’s increasingly antagonistic standards, the speech was an extraordinary combination of bluster and menace, mixing conspiratorial riffs against an American-led “neocolonial system” with an appeal to the world to see Russia as the leader of an uprising against American power.

He referred to “the ruling circles of the so-called West” as “the enemy” — a word he rarely uses in reference to the West — and struck a tone of anger and defiance. And he again raised the specter of nuclear weapons, which the Kremlin has made veiled threats about using, noting in a cryptic aside that the atomic bombs the United States dropped on Japan in 1945 had “created a precedent.”

“Not only do Western elites deny national sovereignty and international law,” he said in the 37-minute address. “Their hegemony has a pronounced character of totalitarianism, despotism and apartheid.”

Western leaders have condemned Russia’s annexations as illegal, and the “referendums” that preceded them — purporting to show overwhelming local support for joining Russia — as fraudulent. President Biden said “the United States will always honor Ukraine’s internationally recognized borders.”

In the United Nations Security Council, 10 of 15 nations voted on Friday in favor of a U.S.-Albania resolution condemning Moscow’s actions, but Russia exercised the veto power it holds as a permanent member. Mr. Putin’s sometime allies, China and India, which have expressed growing uneasiness with his war on Ukraine, were among four nations that abstained; only Russia voted against the resolution.

Ukraine’s government has rebuffed Mr. Putin’s claims and vowed to retake territory captured by Russia in the east and south. “Everything will be Ukraine,” President Volodymyr Zelensky wrote on Friday on the Telegram social network.

In a video, Mr. Zelensky accused the Kremlin of trying to “steal something that does not belong to it,” adding “Ukraine will not allow that.”

He also announced that he was fast-tracking his country’s application to join NATO — a move that Russia vehemently opposes and that faces steep hurdles, given that admission to the alliance requires unanimous consent from all 30 member nations.

Mr. Putin insisted that Russia’s position on annexing the four territories was nonnegotiable, adding that it would defend them “with all the forces and means at our disposal.”

“I call on the Kyiv regime to immediately cease-fire and all military action,” he said, and “to return to the negotiating table.”

“But we will not discuss the decision of the people of Donetsk, Luhansk, Zaporizhzhia and Kherson,” he went on, referring to the four Ukrainian regions being annexed. “It has been made. Russia will not betray it.”

Earlier Friday, Russia unleashed one of the deadliest attacks against Ukrainian civilians in weeks with a strike in the Zaporizhzhia region, one of those Russia has said it is annexing. The attack killed 25 people and injured another 66, Ukraine’s prosecutor general said. It was part of a flurry of strikes against Ukrainian towns just hours before Mr. Putin spoke.

Speaking at the White House, Mr. Biden said “America and its allies are not going be intimidated by Putin and his reckless words and threats.” But for Washington and its European allies, Mr. Putin’s decision to escalate his rhetoric, while insisting he was ready to negotiate, sets up difficult choices about how much direct confrontation they are willing to risk with Moscow.

The military draft that Mr. Putin declared last week means that he will soon have more men to send to the front line, while his claims of an existential conflict appeared designed to prepare his populace for more trying times ahead.

“The West has to think what is the final price it is ready to pay for Ukraine,” said Alexander Baunov, a Russian international policy expert with the Carnegie Endowment for International Peace. “And it is a very serious question because we don’t know the further appetites of Putin’s Russia.”

But Mr. Putin faces monumental challenges of his own. Conscription has proved so unpopular that on Thursday he took the rare step of acknowledging on national television mistakes by his government in how it was carried out.

Tens of thousands of young men are fleeing Russia and the draft, braving miles-long lines at the borders with Georgia and Kazakhstan, a signal that many Russians are not buying Mr. Putin’s arguments for the invasion of Ukraine. And the chaos of the draft has dealt another setback to Russia’s sanctions-scarred economy.

Mr. Putin’s answer on Friday was to respond with threats, jingoism and conspiracy theories. In the evening, he appeared at a concert and rally in Red Square and, standing before St. Basil’s Cathedral, led the crowd in a chant of “Hooray! Hooray! Hooray!”

“The truth is behind us, and in truth there is strength, which means victory!” Mr. Putin said at the end of his brief address at the rally, borrowing a catchphrase from a 2000 Russian crime film. “Victory will be ours!”

In his speech at the Kremlin, Mr. Putin cast the conflict with the West in even more severe terms than he had previously, reeling off centuries of Western military actions to denounce the American-led world order as fundamentally evil, corrupt and set on Russia’s destruction.

“The repression of freedom is taking on the outlines of a reverse religion, of real Satanism,” Mr. Putin said, asserting that liberal Western values on matters like gender identity amounted to a “denial of man.”

But Mr. Putin offered few new details on the matter that is now perhaps of greatest concern in Western capitals — whether, and at what point, he might use weapons of mass destruction to force Ukraine to capitulate. His spokesman said earlier in the day that after the annexation of the four regions — a move that virtually no other country is expected to recognize — an attack on those regions would be treated as an attack on Russia.

Without saying so directly, Mr. Putin hinted that the role of nuclear weapons in war is on his mind. Describing the West as “deceitful and hypocritical through and through,” Mr. Putin noted that the United States was the only country to have used nuclear weapons in war. He then added: “By the way, they created a precedent.”

Mr. Putin was appealing to three key audiences. To Russians, he sought to justify the expanding hardship his war has been causing by insisting they were fighting for their survival. To the West, he worked to telegraph his determination that he was unbowed by sanctions or arms deliveries to Ukraine, and would keep fighting — with the veiled threat of Russia’s enormous nuclear arsenal in the background.

And to the rest of the world, Mr. Putin sought to cast himself as the leader of a global movement against the “Western racists” he claimed were imposing American hegemony. The West, he claimed, had not changed from the centuries past in which it brutally colonized other countries and fought wars to gain economic advantage.

Western countries, he insisted, had “no moral right” to condemn the annexation of parts of Ukraine.

“The Western elites remain colonizers as they always were,” Mr. Putin said. “They have divided the world into their vassals — the so-called civilized countries — and everyone else.”

As Mr. Putin spoke, a crowd gathered on Red Square for the concert and rally. Russian media reported that Moscow universities had directed students to attend. Pro-Kremlin pop music performers belted out nationalist songs from a stage that said “Russia!” and was flanked with banners reading “Choice of the people!” and “Together forever!”

At one point, a young woman in an orange sweatshirt took the stage, describing herself as a volunteer helping people in Russian-occupied Ukraine. Her husband had been drafted a week ago, she said.

“I’m not moping and will wait for him and support him,” she said. Appearing to hold back tears, she added: “I call on you, women: support your husbands, sons and fathers. Everything will be OK.”

Oleg Matsnev contributed reporting.