Eight months into his second term, President Trump has made a declaration about Ukraine that sounded vaguely like the ones his predecessor, President Joseph R. Biden Jr., used to make. With the right mix of courage, ingenuity and weapons from NATO, he asserted on Tuesday, Ukraine could force Russia to retreat from the territory it has seized in three and a half years of brutal war.
But scratch the surface, and a deeper desire seemed buried in Mr. Trump’s reversal of position during the U.N. meetings in New York this week. Mr. Trump appears to want to wash his hands of the Ukraine conflict, after having no success bringing President Vladimir V. Putin to the negotiating table, and a dwindling chance of acting as mediator between the two warring parties.
Like many policy declarations by Mr. Trump, it is hard to divine his true beliefs, and impossible to assure he will not change position again. He is nothing if not mercurial. His foreign policy views, former aides say, are more often driven by pique and a sense that he has been disrespected than by strategic analysis.
And his own key advisers seemed taken by surprise by his sudden conclusion that Ukraine, after years of struggle, is suddenly capable of winning back the one-fifth of the country that President Vladimir V. Putin’s troops now occupy.
On the same afternoon that Mr. Trump issued his conclusion on Ukraine, Secretary of State Marco Rubio — who is also acting as national security adviser — repeated the administration’s old maxim that the war in Ukraine “cannot end militarily,” predicting that “it will end at a negotiating table.” The White House, asked to clarify the contradictions between the two statements, did not immediately respond to a series of emailed questions.
It is possible, said several experts who have followed the president’s search for tactical advantage in dealing with Russia and Ukraine, that nothing much has changed here at all.
“The reversal is one of analysis and not policy,” said Richard Fontaine, the chief executive of the Center for New American Security and a former aide to Senator John McCain. “Trump is oscillating between extreme views of the situation — previously, Ukraine couldn’t win because Kyiv didn’t have cards to play, and now it can win all of its territory back because Russia is merely ‘a paper tiger.’”
“Either view seems to minimize America’s role in the war,” concluded Mr. Fontaine, who has written extensively about strategies to help Ukraine. “He suggests no change in U.S. policy. There is no new call for a cease-fire or peace agreement, no new sanctions, no new deadlines and no new military support for Ukraine, beyond the weapons NATO buys from the United States.”
For those reasons, American allies at the United Nations seemed unimpressed. Britain’s prime minister, Keir Starmer, noted during a news conference with Mr. Trump in Britain a week ago that Mr. Putin responded only to heavy pressure led by the United States; Mr. Trump’s suggestion that he would stand on the sidelines, one senior British official said, did not seem likely to change the status quo.
Senator Mitch McConnell, the Kentucky Republican and former Senate majority leader, who has been a longtime supporter of Ukraine, issued a statement after Mr. Trump’s announcement that first welcomed the president’s seeming support for Ukraine — and then accused his own administration of undermining that support.
“The president has identified Russia as the aggressor,” he wrote, adding that “his administration should act accordingly. If senior Department of Defense officials continue to blame NATO allies for provoking Russia, freeze or limit security assistance to Ukraine, or oppose further investments in security cooperation with Ukraine and vulnerable NATO allies, in defiance of the support expressed overwhelmingly by House Republicans last week, they are undermining President Trump’s efforts to end the war.”
He added: “The commander in chief should not tolerate such freelance policymaking that weakens his leverage and undercuts investments in peace through strength.”
While Mr. McConnell was careful not to be too specific, he appeared to be referring to announcements by Defense Secretary Pete Hegseth and his top aides about reductions in military training and other help to vulnerable nations sharing a border with Russia. That has led some experts to urge a focus on what the administration spends, rather than what the president says, in order to measure American support for Ukraine.
Laura Cooper, a former senior official in the Pentagon during the Biden administration who was responsible for Russia and Ukraine, noted on Wednesday that during the first three years of the war, there was “a roughly 50-50 split in U.S. and European security assistance to Ukraine,” both to fight the war and to build a military force that could deter Russia in the future. “Today, the U.S. share of assistance has vanished. The Europeans alone can help keep the Ukrainians in the fight, but it’s unclear how they can actually help them win the peace without U.S. aid.”
Mr. Putin, she noted, “is always watching U.S. support for Ukraine in matériel not just rhetorical terms. No other country deters Russia like the United States.”
For his part, Mr. Zelensky did his best to sound enthusiastic about the president’s rhetorical shift, which he called a “game changer.”
Mr. Zelensky had some reason to celebrate: His long-running effort to get back into Mr. Trump’s good graces, after their famous confrontation in the Oval Office in February, had paid off. Mr. Trump was no longer pressuring him to give up land for peace, which could be politically suicidal for the wartime president. Moreover, Mr. Trump, openly annoyed at Mr. Putin, may have been pressuring the Russian leader to make concessions, rather than Mr. Zelensky.
(If so, the Kremlin sounded unimpressed: Dmitri S. Peskov, the Kremlin spokesman, said dismissively, “The assertion that Ukraine can win back something by fighting is mistaken.” Then he told a Russian radio station that “Russia is in no way a tiger. It’s more associated with a bear. And there is no such thing as a paper bear.”)
But after Mr. Trump left New York, it was clear that Mr. Zelensky was back where he had always been: in severe need of money, technology, intelligence, fresh troops and support for a war that has lasted almost as long as America’s involvement in World War II.
In his speech to the United Nations on Wednesday, Mr. Zelensky told the representatives of the member nations that he had learned a few things. The conflict with Russia was worsened by the “collapse of international law and the weakness of international institutions,” a seeming reference to the world body itself.
Security, he said, comes not from laws and resolutions, but “friends and weapons.”
“Ukraine is only the first, and now Russian drones are already flying across Europe, and Russian operations are already spreading across countries,” Mr. Zelensky said, a reference to incidents this month in which Russian drones flew over Poland and Russian fighter jets lingered in Estonian airspace for 12 minutes, testing NATO defenses.
Mr. Zelensky has always known that his most powerful argument is that, if successful in Ukraine, Mr. Putin will not halt there.
“Stopping Russia now is cheaper than wondering who will be the first to create a simple drone carrying a nuclear weapon,” he said.