United Nations: Top-ranked tennis player Roger Federer was named a goodwill ambassador for the UN children's agency UNICEF, joining footballer David Beckham, pop singer Shakira, action film star Jackie Chan and other celebrities in the campaign to draw attention to the world's neediest children. The 24-year-old Federer, who on Sunday won the Nasdaq-100 Open in Key Biscayne, Florida, appeared shy and slightly embarrassed when the crowded hall at UNICEF headquarters gave him a standing ovation when he officially signed up as ambassador. "We are given a chance to visit so many different countries and cultures and interact with people from all walks of life," Federer said of tennis pros. "It is our responsibility to connect with the real world beyond our sport, to use our fortune to make a difference in the lives of those who most need it." Federer appeared less than 24 hours after his victory on Sunday over Croatia's Ivan Ljubicic. His browned face still bore a clear tan line from the trademark headband he wears in matches. He gently chided one questioner who asked him why he felt it was important to appear in New York after such a physically gruelling week. "OK, the schedule is hectic, but why? It's because I won the tournament," Federer said. "You know, if I would have lost earlier, I would have had an easy schedule. So it's a great problem to have that I have this busy schedule." Federer joins about two dozen other celebrities from around the world as a goodwill ambassador for UNICEF.