Mr. Biden, who has since left Kyiv, is scheduled to meet with President Andrzej Duda of Poland on Tuesday morning and deliver a speech from the Warsaw Castle later that afternoon. President Vladimir V. Putin of Russia is expected to speak the same day, creating a split-screen image of the two leaders making their separate arguments about the war.
Russia’s invasion of Ukraine has turned into a long, brutal slog, with Ukrainian forces — backed by the United States and other Western allies — putting up a fierce fight. But Mr. Putin’s forces, bolstered by an army of private soldiers conscripted into service, have begun a fresh assault on those positions even as Russia continues its practice of bombarding civilian infrastructure in cities across Ukraine.
Russia’s state media quickly started using Mr. Biden’s visit as evidence of the Kremlin’s claim that the West is waging a proxy war against Russia. “We’re not at war with Ukraine, certainly not with the Ukrainian people,” the RIA Novosti state news agency quoted an analyst as saying. “The Kyiv authorities embody an instrument of the collective West.”
Mr. Biden’s visit to Kyiv recalled the secret missions flown by Presidents George W. Bush, Barack Obama and Donald J. Trump to Iraq and Afghanistan during the height of the wars in those countries. But bringing a president into Ukraine without the sort of American troop presence that was on the ground in Iraq and Afghanistan, much less control of the airspace, presented a security challenge of a vastly different magnitude. American warplanes were spotted flying over Poland near the border, but officials said they did not enter Ukrainian airspace.
Mr. Biden’s visit comes after Mr. Zelensky made his own high-profile visit to Washington just before Christmas Day last year, his first trip outside Ukraine since the start of the Russian invasion, as he pleaded with Western leaders to provide more support.
Mr. Zelensky made that appeal during meetings with Mr. Biden at the White House and in an emotional speech to Congress. Like Mr. Biden’s trip to Ukraine, Mr. Zelensky’s visit was kept secret until the eve of his arrival for security reasons.
Two days after Mr. Zelensky’s speech, Congress approved nearly $50 billion in additional emergency aid for Ukraine, much of it military equipment aimed at allowing the country to fight back against Russia. That pushed the total amount of U.S. aid approved for Ukraine since the war started past $100 billion.