The diary and a revealing letter written by notorious Auschwitz death camp doctor, Josef Mengele, are to be sold at auction in the US.

The auction house initially hoped to realise a price of $60,000 for the rare documents when the initial auction was held on January 20th, but so far no one has shown an interest.

The chilling documents prove Mengele was the SS officer who performed bizarre medical experiments on camp inmates.

Mengele, also known as "the angel of death," sent thousands of Jews to the gas chambers and operating theatres of Auschwitz.

His diary was written in the 1960s when he was hiding in South America.

The document, which had apparently been in the possession of Mengele's son, concentrate on subjects such as the Nazi natural selection doctrine, breeding programs and genetics.

Mengele, who was 49 when he began his diaries, wrote: "I see how right my plans have been all along and I understand now that following people's advice mostly results in irreparable nonsense. But I refuse to pass guilt onto others: I was solely responsible for my decisions."

On his ideas of natural selection, he stated: "The real problem is to define when human life is worth living and when it has to be eradicated. There's no good or bad in nature. There's only appropriate or inappropriate. Both sides receive equal chances. Nevertheless, nature provides a strainer. Things that are inappropriate fall through since they lose in the struggle for survival."

He further said: "Everything will end in catastrophe if natural selection is altered to the point that gifted people are overwhelmed by billions of morons. We have to prevent the rise of the idiot masses. Inferior morons should be exterminated. We have to make sure that nature's suspended eradication will continue through human arrangements. Birth control can be done by sterilizing those with deficient genes."

While it is not known exactly how the world's most hunted Nazi war criminal died, it is believed Mengele drowned or suffered a stroke in Bertioga, Brazil.