Daegu - US sprint legend Michael Johnson on Friday backed the right of South African double amputee Oscar Pistorius to run in the world championships because the rules state he can do so.
Known as the 'Blade Runner' because he runs with carbon fibre prosthetic running blades, Pistorius was selected for the 400 metres and is part of his country's 4x400m relay squad.
Cleared three years ago to run against able-bodied athletes, the 24-year-old four-time Paralympic gold medallist left it late to qualify, going under the requisite time at his final chance with a personal best of 45.07 seconds.
Johnson, who won four Olympic gold medals and six individual world golds in a stellar career, described Pistorius' presence at the world championships in Daegu, South Korea, as a "groundbreaking moment in athletics".
"I've been clear about my position from the very beginning and Oscar and I have talked about it. I support Oscar because the rules state that he can compete," said Johnson at a press event with Pistorius.
"I want to see him do the best he can possibly do."
The issue of whether the blades give an advantage over able-bodied athletes is back in the spotlight following Pistorius's qualification for the worlds.
"My position on the rule is that probably more work should be done", Johnson added.
"Now that there is this controversy again I think people are unsure but as I said, I focus on the rules. The rules are that he's allowed to run," he said.
Pistorius said he was clear in his own mind that he gained no advantage through the use of his prosthetic limbs.
"We have been through a lot of testing," he said, adding that scientists had concluded there was "no net advantage" from the use of the limbs.
"I really do believe in the purity of sport... For me it was an important thing to make sure that I don't have any advantage," he said.
The South African, who said qualifying for next year's London Olympics had become "an obsession", admitted that running in the world championships, which start Saturday, was daunting.
"My expectations for myself are to run consistently. I think that for me is more important than anything else. If I can come close to my personal best I will be very happy," he said.
"The one thing I really need to do is gain as much experience as I can from this competition."
Johannesburg-born Pistorius had both legs amputated below the knee when he was 11 months old because of a congenital condition that meant he was born without fibulae - lower leg bones.
Pistorius failed to qualify for the 400m at the 2008 Beijing Olympics having been given the green light to attempt to qualify after the Court of Arbitration for Sport overturned a ruling by the International Association of Athletics Federations (IAAF) that his blades gave him an unfair advantage.
The IAAF said earlier Friday that Pistorius would have to run the first leg for his country should he wish to take part in the 4x400m relay.
The athletics world governing body said that to "avoid danger" to other runners, Pistorius would run the first leg in his lane before handing over the baton to the second runner, who then breaks the lane order.