Russian chess master and political activist Garry Kasparov has compared President Vladimir Putin's "one-man dictatorship" to the rule of Adolf Hitler, warning that if the West fails to stop him now the price to do so could get much higher.

Kasparov also argued that Western leaders should not try to appease Putin in a search for strategic ground with him on issues like Iran's nuclear program and the war in the Middle East. He says Putin thrives on instability, and that trouble in the Middle East benefits his regime by boosting oil prices.

Kasparov, a dissident who now lives in New York, spoke Thursday at the Warsaw Security Forum, where his strong criticism of Putin drew applause from participants.