President Trump on Thursday sharpened his threat to impose sanctions on Russia over its war in Ukraine, even while acknowledging that the weapon he once argued worked on everyone — the threat of financial ruin — may have no effect on its president, Vladimir V. Putin.

“We’re going to put sanctions,” he said, even though a deadline he gave Moscow this week to seriously engage on a cease-fire had not yet passed. “Russia? I think it’s disgusting what they’re doing,” he said, apparently referring to its continued bombing of Ukraine.

Mr. Trump’s comments came after Secretary of State Marco Rubio acknowledged in an interview with Fox News Radio that the administration held secret talks with Russia this week — “not with Putin but with some of Putin’s top people” — and made no progress on a cease-fire. Mr. Trump said he was dispatching his special envoy, Steve Witkoff, to Russia again, but the last visit that Mr. Witkoff, a fellow real estate investor, paid to Mr. Putin proved fruitless.

Administration officials gave no reasons to believe the latest engagement with Russia would be any more useful. And Mr. Trump himself, usually a true believer in the power of economic sanctions to alter the decisions of foreign leaders, admitted for the second time this week that Mr. Putin appears to be immune.

“I don’t know that sanctions bother him,” he said on Thursday.

Nonetheless, Mr. Trump has now executed a 180-degree turn on Russia, at least in tone, in roughly 180 days.

He came to office questioning whether Russia was truly the invader of Ukraine, and hinting that the Ukrainians were responsible for their own troubles. His famous blowup with President Volodymyr Zelensky in the Oval Office in February led him to briefly cut off aid to the Ukrainian military. His defense secretary, Pete Hegseth, declared that Ukraine would never join NATO — a reversal of stated American policy — and Vice President JD Vance spoke out against arming the Ukrainians. Russia was exempted from most tariffs.