BlackBerry has launched a new smartphone as the Canadian company tries for a comeback. Chief executive John Chen unveiled a large-screen, square sized phone called the Passport to a Toronto audience on Wednesday. London and Dubai also hosted launch events. No event was held in the U. S. where analysts say there is little demand or carrier interest. BlackBerry lost relevance as a dominant smartphone company following the launch of Apple's iPhone and the introduction of Google-powered Android phones. Chen says the Passport will be available in the U.S. on AT&T on an exclusive basis by the end of the year. It is also available for $599 for a limited time on Amazon. Chen says he expects to release a more popular phone called the "Classic" later this year.