President Biden used his first speech at the United Nations since the invasion of Ukraine to accuse one man, President Vladimir V. Putin of Russia, of seeking to “erase” another nation from the map and of trying to drag the world back to an era of nuclear confrontation.
Hours after Mr. Putin mobilized reservists for Ukraine and issued new threats to deploy Russia’s nuclear arsenal, Mr. Biden drew a sharp contrast between Russia and the West and described a growing competition with China as it pursues its own authoritarian vision.
“Let us speak plainly,” Mr. Biden said as he opened his address to the General Assembly, accusing Mr. Putin of violating the U.N. Charter. “A permanent member of the United Nations Security Council invaded its neighbor.”
The war, Mr. Biden added, is about “extinguishing Ukraine’s right to exist as a state.”
“If nations can pursue their imperial ambitions without consequences,” Mr. Biden went on, the post-World War II order crumbles. “We will stand in solidarity against Russia’s aggression.”
The scope and scathing nature of Mr. Biden’s attacks on Mr. Putin were startling; they appeared to be the most direct and sustained focus on a single adversary by an American president at the United Nations since 2002, when President George W. Bush called the Iraqi government of Saddam Hussein a “grave and gathering danger.”
Mr. Biden told the leaders “we do not seek a Cold War” or to ask other nations to choose between the United States and “any other partners.”
Yet the world he described had echoes of the Cold War era. Mr. Biden cast the United States and its allies as the protectors of a fragile global order that has endured since World War II, while seeking to reassert American leadership on existential issues like warming temperatures and faltering food supplies. And he portrayed Russia as the chief threat to global peace, describing the Russian leader’s warnings just hours before as “irresponsible nuclear threats” and warning him against following through.
“A nuclear war cannot be won,” Mr. Biden said, “and must never be fought.”
That phrase, used by Ronald Reagan and Mikhail S. Gorbachev in 1985, was repeated by all the major nuclear powers in a joint statement on Jan. 3, just seven weeks before Mr. Putin’s invasion set off perhaps the biggest concerns about the use of nuclear weapons since the Cuban Missile Crisis, 60 years ago.
Mr. Biden’s speech, on the second day of the U.N.’s annual gathering of world leaders, came at a moment of extraordinary peril and upheaval, with food shortages, floods, droughts, record heat, a pandemic and inflation. In many of those arenas, the U.N. has seemed either powerless or paralyzed, in part because Russia, as a member of the Security Council, is able to veto resolutions condemning its actions. Mr. Biden seized on the moment to call for U.N. reforms, though few seem imminent.
With war raging in Ukraine, the conflict dominated the annual gathering of world leaders, though Mr. Putin and Xi Jinping of China both skipped the event. Ukraine’s president, Volodymyr Zelensky, addressed the General Assembly in a pretaped video, recorded from Ukraine and in English.
“A crime has been committed against Ukraine, and we demand just punishment,” Mr. Zelensky said, describing the death and destruction that “Russia provoked with its illegal war.”
Mr. Zelensky said the world must continue to “unite around the one who fights against armed aggression.”
Earlier this month, as Ukrainian forces seized back territory in Ukraine’s northeast and, bit by bit, in the south, some world leaders thought Mr. Putin might withdraw, declaring he had met his goals.
Instead, hours before the leaders came to the podium of the General Assembly, he doubled down, calling for a mobilization of 300,000 Russian reservist troops and making it clear he had no intention of giving up his quest to eliminate Ukraine as an independent country.
News of Mr. Putin’s combative speech was coming across the mobile phones of leaders and diplomats as they made their way through the blocked-off streets of Manhattan’s East Side. Many were struck by the bluntness of his nuclear threat, which he said was “not a bluff.” Others described it as rooted in despair, as Mr. Putin tries to recover from humiliating retreats.
Chancellor Olaf Scholz of Germany said in an interview on Wednesday that Mr. Putin’s comments reflected how badly he had miscalculated in invading Ukraine.
“He’s misguided, he underestimated the situation and he’s desperate,” Mr. Scholz said.
The allies largely stuck together.
The vice president of the European Commission, Josep Borrell, vowed new sanctions on Moscow, though the menu of options available is diminishing, short of complete expulsion from global transactions of what was last year the world’s 11th largest economy. Mr. Borrell said he would convene an extraordinary meeting of Europe’s foreign ministers in New York to discuss the developments.
“Putin says that he is ready to use all arms at his disposal and when someone says ‘all’ he also means explicitly nuclear arms,” Mr. Borrell said. “This is something that the international community cannot accept. The United Nations this week has to react.”
Mr. Biden also criticized the governments of Iran and China for their human rights records.
He said the United States stood with “the brave citizens and the brave women of Iran, who right now are demonstrating to secure their basic rights” — a reference to the protests that have erupted in Iran over the death in custody of Mahsa Amini, a 22-year-old woman who was arrested by the country’s morality police last week, allegedly for violating dress codes.
And with talks stalled on restoring the 2015 Iran nuclear deal, which former President Donald J. Trump abandoned, Mr. Biden implicitly threatened to use force if necessary to prevent Iran from developing nuclear weapons, but said that he wanted to prevent conflict.
“We will not allow Iran to acquire a nuclear weapon,” Mr. Biden said, adding, “I continue to believe diplomacy is the best way to achieve this outcome.”
Earlier on Wednesday, Iran’s president, Ebrahim Raisi, made his debut before the General Assembly, insisting that his country was a model of justice and human rights.
Mr. Raisi’s remarks, in a long speech that mixed religious sermons and political rhetoric, made no mention of the widespread anti-government protests that had elicited a crackdown by authorities, nor the death of the young woman that had sparked them.
Several heads of state recounted the mounting toll of climate change on impoverished people around the world, including cyclones in Madagascar, drought in the Horn of Africa and flooding in Pakistan.
Mr. Biden spoke of the $370 billion in new spending and tax incentives meant to reduce greenhouse gas emissions that he signed into law last month as evidence of American leadership on fighting climate change. And he announced $2.9 billion in new spending by the United States to address global food insecurity, which has been exacerbated by both the war in Ukraine and climate change.
But leaders from Africa and elsewhere used their speeches to push wealthy nations to do more, faster, to stem global temperature rise.
“Africa’s young people, the entire continent, are waiting for polluting countries to comply with promises made,” President Andry Rajoelina of Madagascar told the assembly.
Mr. Biden acknowledged that debt at the start of a meeting on Wednesday afternoon with United Nations Secretary-General António Guterres, telling Mr. Guterres that “great polluting nations of the world like ours owe an obligation to the nations that are suffering the consequences of global warming.”
Mr. Biden met Wednesday with the new British prime minister, Liz Truss, discussing the war and a trade dispute stemming from Britain’s decision to leave the European Union, which Mr. Biden has warned could jeopardize a longstanding peace accord in Northern Ireland. The president also met with President Emmanuel Marcon of France and delivered remarks to the Global Fund on the worldwide fight against H.I.V./AIDS, tuberculosis and malaria.
Mr. Zelensky’s address aired soon after Mr. Biden finished at the Global Fund, returning the day’s focus to Mr. Putin and the damage inflicted by the invasion of Ukraine.
Mr. Zelensky called on the United Nations to hold Russia accountable by creating a special tribunal and said Russia should be deprived of its veto right in the U.N. Security Council.
“Russia should pay for this war,” he said, “with its assets.”
Michael Crowley, Alan Yuhas and Edward Wong contributed reporting.