Pistorius refuses to accept he murdered Steenkamp
The former athlete makes the claim in an exclusive interview with British television channel ITV.
The former athlete makes the claim in an exclusive interview with British television channel ITV, which is to be broadcast in South Africa on M-Net tomorrow night.
Pistorius was initially convicted of culpable homicide for the 2013 crime but the Supreme Court of Appeal convicted him of murder last year.
In the interview, Pistorius tells ITV that he would serve 10 years in jail for killing Steenkamp, but refuses to accept that he murdered her.
WATCH: Barry Steenkamp: Oscar Pistorius must pay
He recalled the night of the shooting.
"I'm screaming and I'm praying to the Lord. God please, please, please as I opened the toilet door, immediately when I saw Reeva, she was over the toilet."
He says he realised the extent of Steenkamp's injuries.
"At that point I knew I'd killed her, I knew she was dead and I went down on my knees and put her on me."
The convicted murderer has used the exclusive interview to challenge some of the allegations made against him by the State during his trial and in the public domain.
During sentencing, State prosecutor Gerrie Nel argued that Pistorius disrespected the court by granting a television interview, but refused to testify.
In the interview, Pistorius explains why he struggles to walk on his stumps.
"I don't have balance [when I'm on my stumps] and that's why I put on my legs when I wake up in the morning. It's painful to walk far distances. There's been an argument why if the door was right there in the bedroom I didn't get Reeva and run away. I can't quite run away and I can't defend myself."
Click here to view 3 snippets of Oscar Pistorius's interview with ITV.