"I think I'm ready for the 800," Semenya said after sprinting to a 54.03sec victory at the Bellville Stadium on the outskirts of Cape Town in the third meeting in a national athletics series.
"It's what I'm training for so I'm just going to train hard so I can retain my title. I think I'm good enough to retain my title."
Semenya, 20, said she was still recovering from the back injury that stopped her competing at the Commonwealth Games in India last October.
"I'm trying to heal my injury because I've not yet healed," she told journalists after the race.
Semenya said she had run the shorter distance race to get some track time under her belt and was delighted to beat her target time.
"I'm happy with the time," she said.
Semenya, who underwent gender verification tests following her Berlin world championship triumph and did not race for almost a year, plans to defend the world title in South Korea in August.
The probe into her gender was made public by the IAAF shortly before the athlete won a gold medal at the 2009 world championships, thrusting her into the global spotlight.