President Trump has described President Vladimir V. Putin as “savvy” and “genius” for invading Ukraine, while bragging about his “very, very good relationship” with the autocratic Russian leader.

Mr. Trump has helped the Kremlin recast Ukraine as the villain rather than the victim in the war, and has publicly berated President Volodymyr Zelensky of Ukraine in the Oval Office and blamed him for starting the conflict and undermining peace negotiations.

But four months into his term, Mr. Trump’s preference for praising and excusing Mr. Putin has not stopped the bloodshed in a war he once bragged he would end in just 24 hours.

After weeks of Mr. Trump claiming he could leverage his relationship with the Russian leader to bring peace, Mr. Putin’s continued aggression has prompted even Mr. Trump to question whether he has been strung along.

“We’re going to find out whether or not he’s tapping us along or not and if he is we’ll respond a little bit differently,” Mr. Trump told reporters in the Oval Office on Wednesday. “I’m very disappointed at what happened, a couple of nights now where people were killed in the middle of what you would call a negotiation.”

After a call between the American and Russian leaders last week yielded no breakthroughs, Mr. Trump appeared ready to distance himself from negotiations altogether and said it would be up to Russia and Ukraine to stop the fighting.