MOSCOW — President Vladimir V. Putin of Russia on Friday unleashed perhaps his strongest diatribe against the United States yet, using an international meeting of Russia experts to sell Moscow’s view that American meddling has sparked most of the world’s recent crises, including those in Ukraine and the Middle East.

Instead of supporting democracy and sovereign states, Mr. Putin said during a three-hour appearance at the conference, the United States supports “dubious” groups ranging from “open neo-fascists to Islamic radicals.”

“Why do they support such people,” he asked the annual gathering known as the Valdai Club, which met this year in the southern resort town of Sochi. “They do this because they decide to use them as instruments along the way in achieving their goals, but then burn their fingers and recoil.”

The goal of the United States, he said, was to try to create a unipolar world in which American interests went unchallenged.