President Trump says he wants a quick cease-fire in Ukraine. But President Vladimir V. Putin of Russia appears to be in no rush, and the blowup on Friday between Mr. Trump and Ukraine’s president may give Russia’s leader the kind of ammunition he needs to prolong the fight.

With the American alliance with Ukraine suffering a dramatic, public rupture, Mr. Putin now seems even more likely to hold out for a deal on his terms — and he could even be tempted to expand his push on the battlefield.

The extraordinary scene in Washington — in which Mr. Trump lambasted President Volodymyr Zelensky of Ukraine — was broadcast as the top story on state television in Russia on Saturday morning. It played into three years of Kremlin propaganda casting Mr. Zelensky as a foolhardy ruler who would sooner or later exhaust the patience of his Western backers.

For the Kremlin, perhaps the most important message came in later remarks by Mr. Trump, who suggested that if Ukraine did not agree to a “cease-fire now,” the war-torn country would have to “fight it out” without American help.

That could set up an outcome that Mr. Putin has long sought, at the cost of tens of thousands of Russian lives: a dominant position over Ukraine and wide-ranging concessions from the West.

In fact, Mr. Trump’s professed attempts to end the war quickly could intensify and prolong it, experts warned. If the United States is really ready to abandon Ukraine, Mr. Putin could try to seize more Ukrainian territory and end up with more leverage if and when peace talks ultimately take place.