THE Reebok Challenge with Michael Chang has developed into a very successful regional tennis programme after only one year, with a record nine countries set to participate in this year's series. The Challenge is a series of junior tournaments being staged throughout Asia and hosts of the 1992 events were Hongkong, Japan, South Korea, Malaysia and Taiwan. China, Indonesia, Thailand and the Philippines will also be running their own tournaments this year, making the Challenge the biggest junior tennis programme in the region. Singapore players will be invited to take part too. The Challenge, developed in association with star American-Chinese player Chang, was introduced last year to give aspiring youngsters in Asia the opportunity to play competitively. It was aimed at developing the sport in the region and as an extra incentive, the top two boys and girls are invited to attend an exclusive tennis clinic by Chang in Melbourne. The Challenge gets underway in the Philippines tomorrow and the series will continue until November, with the Hongkong tournament scheduled from September 24 to October 3. The top four boys and girls from each tournament will qualify for the Asia-Pacific Championships to be held in the territory from December 27-31. Winners and runners-up of the regional finals will be awarded a trip to compete in the Australian Open junior tournament.