Oscar Pistorius is confident he can run the 400m time he needs to qualify for the Olympics.
South Africa's Olympic Committee say athletes must run the qualifying time three months before the Games.
Double amputee Pistorius, 25, beat the 400m standard of 45.30 seconds in March but needs to repeat that feat and has struggled in recent runs.
But he told BBC Radio 5 live: "My next run should be in the ball park of the qualification time."
Pistorius ran a disappointing 46.86 seconds in Saturday's Prefontaine Classic Diamond League meeting in Oregon and will have another chance to reach the time at next weekend's Diamond League meeting in New York before the African Championships later this month.
"Last year I had a dream year and ran the qualification time," he added.
"But when I got to Europe my first race was terrible. Never in my dreams did I think I would run that badly.
"When I ran again my time came down quite significantly, which I'm very comfortable with.
"Now I'm really excited about the next race. I'm feeling confident."
Pistorius, who runs on carbon fibre blades, beat the qualifying time last July to earn a place at the 2011 World Championships, where he became the first amputee to compete, and won a silver medal as part of the 4x400m relay squad, although he did not run in the final.
He last ran the required time at the Provincial Championships for Gauteng North in a selection event for the South African National Championships in March.
He needs to clock the qualification time before the end of June to earn a place at London 2012.