President Biden blamed President Vladimir V. Putin of Russia personally on Friday for the reported death of the imprisoned Russian dissident Aleksei A. Navalny, and cited the case in pressing House Republicans to approve military aid to Ukraine in its war with Moscow.
But while he once threatened to impose “devastating” consequences on Mr. Putin if Mr. Navalny died in prison, the president conceded that there was not much more he could do after the sanctions and other actions taken in the last two years in response to Russia’s invasion of Ukraine.
“Make no mistake: Putin is responsible for Navalny’s death,” Mr. Biden said in a televised statement from the White House. “Putin is responsible. What has happened to Navalny is yet more proof of Putin’s brutality. No one should be fooled, not in Russia, not at home, not anywhere in the world.”
Asked if Mr. Navalny had been assassinated, Mr. Biden said the United States did not have a full understanding of the circumstances. “The answer is, we don’t know exactly what happened, but there is no doubt that the death of Navalny was a consequence of something that Putin and his thugs did.”
The death of Mr. Navalny came at a delicate moment in America’s confrontation with Russia over its aggression in Europe and repression at home. House Republicans are blocking $60.1 billion in military aid to Ukraine at the behest of former President Donald J. Trump, who himself is boasting that he would “encourage” Russia to attack NATO allies that do not spend enough on their armed forces.
Mr. Biden is seeking to make the case for American leadership in the world and reassure European allies that the United States still has their back. He sent Vice President Kamala Harris and Secretary of State Antony J. Blinken to the Munich Security Conference in Germany this week to defuse fears of an American retreat. But the mood in Munich was dark even before reports of Mr. Navalny’s death. American attendees said everywhere they went, they were besieged by distraught Europeans.
“What we want to hear are real assurances that the Americans are not going to abandon Ukraine and Europe,” Wolfgang Ischinger, a former German ambassador to the United States and longtime impresario at the conference, said before Ms. Harris’s speech. “There is panic in this country.”
Ms. Harris sought to give just such assurances, although there was great skepticism in the hall, where many were already preparing for the prospect of a second term for Mr. Trump if he wins the November election.
“In these unsettled times, it is clear: America cannot retreat,” Ms. Harris told the conference. “America must stand strong for democracy. We must stand in defense of international rules and norms, and we must stand with our allies. That is what represents the ideals of America, and the American people know that is what makes us strong. And make no mistake, the American people will meet this moment, and America will continue to lead.”
Speaking in Washington, Mr. Biden cited Mr. Navalny’s death to press his argument to Congress to pass the security aid to Ukraine and expressed indignation that the House had left for a recess without taking action.
“It’s about time they step up, don’t you think?” he said. “Instead of going on a two-week vacation. Two weeks! They’re walking away. Two weeks! What are they thinking? My God. This is bizarre. And it’s just reinforcing all the concern and almost, I won’t say panic, but real concern about the United States being a reliable ally. This is outrageous.”
It was not clear exactly what had happened to Mr. Navalny, but no one in the Biden administration was taking seriously the official explanation that he simply had lost consciousness and died after taking a walk at his Arctic prison. If he was killed, American officials will have to consider what that says about Mr. Putin at this moment. With events seemingly going his way in Washington lately, some analysts said, Mr. Putin may have felt more impunity to act against his most prominent internal challenger without fear of penalty.
Nearly three years ago, Mr. Biden said he had warned Mr. Putin, during a meeting in Geneva, not to harm Mr. Navalny while he was in prison, adding that no one would buy any Russian cover stories if he did turn up dead. “I made it clear to him that I believe the consequences of that would be devastating for Russia,” Mr. Biden told reporters following the meeting in 2021.
“What do you think happens when he’s saying it’s not about hurting Navalny, all the stuff he says to rationalize the treatment of Navalny, and then he dies in prison?” Mr. Biden said at the time. “It’s about trust. It’s about their ability to influence other nations in a positive way.”
But the president conceded on Friday that it would be hard to deliver those “devastating” consequences because in the years since, Russia’s invasion of Ukraine had prompted the United States and the West to impose broad sanctions and other penalties on Moscow. Nonetheless, Mr. Biden said, “we’re contemplating what else can be done.”
Mr. Biden said Mr. Navalny’s death should remind Americans of the importance of standing up to Mr. Putin and took a swipe at Mr. Trump, who appears likely to be his challenger, for encouraging Russia to attack allies. Mr. Biden, calling that a “dangerous statement,” vowed to stand by Europe against Russian aggression.
The president praised Mr. Navalny’s courage for returning to Russia even after he was poisoned and knew that going back would put him at risk of being sent to prison, as he was.
“He was so many things that Putin was not,” Mr. Biden said. “He was brave, he was principled, he was dedicated to building a Russia where the rule of law existed and where it applied to everybody.”
Steven Erlanger contributed reporting.