The Dubai World Cup will no longer be part of the World Series Racing Championship, officials for the fledgling 14-race series announced.No reason was given for the withdrawal of the Dubai World Cup, but the loss is likely a major blow to the series as it enters its fifth year. Sheikh Mohammed bin Rashid al Maktoum, the mastermind behind the $6 million Dubai World Cup, was the driving force behind the series upon its inception in 1999. Emirates, Dubai's national airlines, sponsored the event for the first three years but dropped out prior to last year's series. A replacement sponsor has not been found.A press release announcing the separation read, "The World Series Committee have expressed gratitude for the contribution of Dubai and His Highness Sheikh Mohammed in particular in the early development of the World Series."The first race for the 2003 series will now be the Audemars Piguet Queen Elizabeth II Cup in Hong Kong April 27.