Malaysian badminton hero Lee Chong Wei on Friday said he has not fully recovered from an ankle injury and is unsure of whether he will be in top form for London, his last chance to win Olympic gold. The world number two, who has been receiving stem cell treatment on torn ankle ligaments sustained at the Thomas Cup in China in May, lost the top ranking to arch-rival Lin Dan of China last month after missing two tournaments. He said the London Olympics, which start on July 27, will be his last and he hopes to regain the number one ranking by winning a gold medal -- the first for him and his country. Asked whether he is confident he will be back in top form in time, he said: \"I\'m not sure.... Now I cannot say I have 100 percent recovered. I still have three weeks. I only concentrate on my game.\" With three weeks to go, the 29-year-old said he was about 80 percent fit. He will leave for England next week. Lee said he has been training six to seven hours a day and is still undergoing rehabilitation for his injury. \"I\'m quite happy with my recovery. I still want to prepare mentally because I have just come back from injury,\" he told reporters after a training session at a stadium in the Malaysian capital Kuala Lumpur. \"I just try my best. I hope I can play well in the Olympics and come out with world number one... I know everybody hopes I can take a gold medal.\" Lee became world number one in 2008 after the Beijing Olympics, where he lost in the final to Lin -- who many consider to be the sport\'s best ever player. Lee said he had decided to play for another two years after the London Olympics, competing in the Commonwealth Games and the Asian Games before retiring. \"I have played for a very long time... It\'s good enough,\" he said.