As the leaders of China, Russia and North Korea gathered for a grand military parade in Beijing, President Trump on Wednesday took pains to brush off the striking show of solidarity among America’s adversaries.

In remarks from the Oval Office, Mr. Trump praised the parade as “beautiful,” and “very, very impressive.”

“I understood the reason they were doing it, and they were hoping I was watching, and I was watching,” Mr. Trump told reporters. “My relationship with all of them is very good. We’re going to find out how good it is over the next week or two.”

The president’s comments came despite mounting frustration that his extraordinary summit with one of those leaders — President Vladimir V. Putin of Russia — has yet to yield any concrete results on the war in Ukraine.

Mr. Trump went into the summit vowing that he would achieve a temporary cease-fire in Ukraine or would impose sanctions designed to hurt Russia’s critical oil and gas exports. He emerged having dropped the cease-fire demand, and imposed no sanctions, while Russia stepped up its attacks on civilian targets.

Mr. Trump has publicly described that meeting as a success, but two associates, who described private conversations on the condition of anonymity, said the president was aggravated that Mr. Putin did not commit to more.