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South African Oscar Pistorius' historic appearance at the World Championships came to an end as he failed to qualify for the 400m final.

The first amputee athlete to race in the competition finished last in his semi-final, clocking 45.39 seconds.

"My biggest goal here was to try and make the semi-final which I was able to do," Pistorius told ³ÉÈË¿ìÊÖ Radio 5 live.

"To have made the final would have been not impossible but it would have taken a miracle."

Olympic and world champion LaShawn Merritt of the United States eased into the 400m final as the fastest qualifier.

Britain's Martyn Rooney failed to make the final after finishing seventh in his semi in 46.09.

Pistorius, a four-time Paralympic champion, got a resounding reception from the 40,000 fans at the Daegu Stadium when he stepped up to the blocks in the third semi-final.

The 24-year-old made his usual slow start, but this time he never recovered, crossing the line last in a time 0.80 secs slower than his heat.

He added: "I think I'm a big realist in the sense that I knew the guys in my race were quicker than me.

"It's been a wonderful opportunity. [It was] not as quick as I wanted to be but it's great to have this platform to run on and it's been an unbelievable experience. I'll be back for the relay."

Pistorius will be allowed to compete in the 4x400m relay - with the heats set to take place on Thursday - providing he runs the opening leg to avoid endangering other athletes with the prosthetics.

Asked whether he could potentially compete at both the Olympics and Paralympics in 2012, Pistorius said: "Yes, most definitely. I've already run one qualification time. I've got to do another between January and June next year but I feel that's very much in reach. I've just got to keep doing what I'm doing."

A congenital condition meant Pistorius was born without fibulae - lower leg bones - and led to the decision to amputate both legs below the knee when he was 11 months old.

As a schoolboy, he preferred rugby union, water polo and tennis but took up running seriously in 2004 after it was suggested as part of his rehabilitation from a rugby injury.

He runs with carbon fibre prosthetic blades in place of his lower legs and was initially banned from competing in able-bodied events by the International Association of Athletics Federation (IAAF).

However, the Court of Arbitration for Sport (Cas) overturned the decision in 2008, paving the way for the South African to compete.

In July, the 'Blade Runner' clocked a personal best time of 45.07 in Italy to qualify for the World Championships just inside the cut-off time.