Cruiserweight world titleholder Oleksandr Usyk will make his first defense -- and his United States debut -- against Thabiso The Rock Mchunu on Dec. 17 at The Forum in Inglewood, California, K2 Promotions announced on Wednesday.Usyk-Mchunu will be televised on HBOs World Championship Boxing (10 p.m. ET/PT) and open a tripleheader that will be headlined by the previously announced farewell fight for 51-year-old legend Bernard Hopkins (55-7-2, 32 KOs), the former middleweight and light heavyweight world champion, who will end his 28-year career against Joe Smith (22-1, 18 KOs) in a 12-round light heavyweight contest.This is a great opportunity, Usyk said. Im very excited to fight for the first time in the United States and on HBO. After winning the world title in September, fighting in America was the next goal and I promise the fans in Los Angeles and those watching on HBO a great performance.Ukraines Usyk (10-0, 9 KOs), a 29-year-old southpaw with a big personality, won the Olympic heavyweight gold medal in 2012 and has moved quickly as a professional.On Sept. 17, Usyk traveled to Poland and won a unanimous decision against hometown fighter Krzysztof Glowacki to take his world title. By winning the 200-pound belt in only his 10th professional fight, Usyk broke the division record for fewest fights needed to win a world title, surpassing the mark held by Evander Holyfield, who won a cruiserweight world title in his 12th fight by outpointing Hall of Famer Dwight Muhammad Qawi in an epic 15-rounder in 1986.(Usyk) wants to be known as a true world champion, the same status the gold medal provided him as an amateur, said Alexander Krassyuk of K2 Promotions Ukraine. Were very thankful to HBO for this opportunity and see this as just the first step towards Oleksandr becoming a superstar in the United States.Usyk was initially supposed to face Bosnias 32-year-old Damir Beljo (22-0, 18 KOs) but Beljo ultimately declined to the fight because he did not believe he had enough time to properly prepare for the bout.Beljos decision opened the door for Mchunu (17-2, 11 KOs), a 28-year-old southpaw from South Africa, who made a name for himself in the United States in August 2013 when he upset Eddie Chambe