The president repeatedly said on the campaign trail that he would bring an end to the war in the first 24 hours of his second term.

The United States said it would pause the delivery of some weapons to Ukraine as the Pentagon conducts a review of its munition stockpiles.

President Trump said on Thursday that a phone call with President Vladimir V. Putin of Russia had not resulted in any movement toward ending the war in Ukraine, adding that he was “not happy” with the conflict grinding on. “I didn’t make any progress with him at all,” Mr. Trump told reporters.