Daegu: Double amputee Oscar Pistorius saw his world 400m dream extinguished on Monday as defending champion LaShawn Merritt eased into the final just a month after returning from a drugs ban.

The controversial South African 'Blade Runner', who runs with carbon fibre prosthetic running blades and was making history as the first amputee to compete at the worlds, finished last in his semi-final heat.

Pistorius received a huge cheer from the South Korean crowd and mouthed 'thank you' to the camera as he lined up to race but could not find the pace he needed, timing 46.19sec to finish 22nd out of 24 runners in the semi-finals.

"I would really have liked to have performed better tonight. My goal was to make the semi-final and I did that. It's been a great experience. Even if I had run faster tonight I wouldn't have made the final," said an upbeat Pistorius.

"I have a lot of respect for the guys who have made the final. It's been a great opportunity and I've learned a lot from this experience.

"I'm a realist so for me to make the final, well I wasn't running close to those times. I never had. This is the championship I have worked for for many years. It's been a massive blessing."

But it was a different story for Merritt, who appeared in awesome form in qualifying quickest in 44.76sec, with what seemed to be plenty in reserve.

"It feels good to have qualified for the final and defend my title tomorrow. I have trained hard to come here and do what I am doing right now. I will give it all out on the track," he said.

"We shall see how the final unfolds. A medal is everybody's goal."

The issue of whether the blades give Pistorius, cleared three years ago to run against able-bodied athletes, an advantage is back in the spotlight following his qualification for the worlds in South Korea.

Pistorius, 24, 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.

Also through to Tuesday's final are Belgian twins Jonathan and Kevin Borlee, Grenadan pair Kirani James and Rondell Bartholomew, Tabarie Henry of the US Virgin Islands, Jamaica's Jermaine Gonzales and Nigeria-born Femi Ogunode of Qatar.

European champion Kevin Borlee said: "It was not easy to run and times were not as good as yesterday. But I am in the final and I am happy. Everything is possible in the final. I will give my best and hopefully I can get a medal."