UPDATE 1-UK PM contender Johnson challenges rival to commit to Oct. 31 Brexit date

Boris Johnson, the front-runner in the race to become British prime minister, has challenged his rival Jeremy Hunt to commit to leaving the European Union on Oct. 31, whether he has agreed to a Brexit deal or not.

"For my part, I have been clear that, if I am elected leader, we will leave on 31 October with or without a deal," he said in a letter to Hunt, which Johnson published on Twitter. "Will you join me in this commitment to leave on 31 October come what may?" Hunt responded in a tweet: "Hi Boris, it's good to talk. But no need for snail-mail, why not turn up to Sky tonight and I'll give you full and frank answers?"

Johnson has refused to debate head-to-head with his rival in an event that had been due to take place on Tuesday evening. Debate host Sky News cancelled the event on Monday after Johnson declined an invitation to appear.