PARIS—The head of the U.K.’s Secret Intelligence Service urged the U.S. not to allow Russia to succeed in Ukraine, warning that it would embolden other authoritarian states across the globe and jeopardize trans-Atlantic security.

Richard Moore, the chief of the British Secret Intelligence Service, known as MI6, believes that if Russian President Vladimir Putin manages to achieve victory and turn Ukraine into a vassal state, he will not stop there,

The head of British intelligence, Richard Moore, during his stay at the summit in Paris, warned that ending the current war would mean a victory for Vladimir Putin and a defeat for the entire Western world.