Usain Bolt is determined not to let the absence of some of his main rivals make him drop his guard as he tries to win back the 100 metres world title he lost two years ago. Bolt, who retained his Olympic title last year, said after arriving in Moscow for the world championships that he was not worried he would repeat the nightmare of Daegu in 2011, when he was disqualified for a false start. "I went to the Olympics, and now I'm back - back to regain my title. I'm even more focused than last time. So I'm going to get it done," the Jamaican said ahead of the championships which begin on Saturday. American Tyson Gay and Jamaican former world record holder Asafa Powell will not compete in Moscow after failing doping tests. Jamaican Yohan Blake will not defend his title because of a hamstring injury. Bolt, who has won six Olympic gold medals and is the 100 metres world record holder, denied their absence would affect his own motivation, pointing out that he had won titles before when big rivals were not competing. "So for me I'm really motivated to go and show the world that even without nobody there, I can still win. So I'm focused, and I'm ready to go," he said. Bolt, whose main rival for the 100 gold is likely to be American Justin Gatlin, made it clear that winning was his priority, not setting a new world record in Sunday's final. "I never predict times, because you never know, it might be like this, you know, overcast, and slightly chilly, or it might just be warm. You never know what can happen, so that's my focus, and that's what I'm going out there to do, and [to] prove to the world that I'm still a champion," he said. Bolt, 26, looked relaxed as he performed a set with DJs at a Jamaican-themed party in the Puma Yard in Gorky Park in central Moscow. He said he would not jump the gun by discussing the doping tests failed by Powell and Gay, saying the full details were not known: "So, I don't want to judge anybody until I hear the final [details]." Bolt won 100, 200 and relay golds in the 2008 and 2012 Olympics. He won the 100 and 200 world titles in 2009 and held the 200 title in Daegu two years later. He said he was open to a proposal by Mo Farah, Britain's Olympic 5,000 and 10,000 metres champion, to race each other over 600 metres. "We don't know if it will happen, but we'll definitely be thinking about it, to see if it possibly could fit in our schedules. So we'll definitely look into it and see what can happen," Bolt said.