New York (AFP) - Mr Nelson Mandela feared and hated his apartheid jailers when he left prison but overcoming that "demon" is a sign of his greatness, former United States president Bill Clinton said Thursday.

The former US president, United Nations leader Ban Ki Moon and Mr Andrew Mlangeni, who was a prisoner alongside Mr Mandela, honoured him in a special ceremony at the UN headquarters as he spent his 95th birthday in hospital.

Mr Clinton said Mr Mandela ended his 27 years in an apartheid jail "a greater man than he went in" but also told how the ordeal had left its mark on the legendary figure.

"Every day was a struggle, I could see it in his eyes even after he became president. Some old demon would rise up and somebody or say something stupid, but he fought it every day," Mr Clinton said at the UN General Assembly.

Mr Clinton told how he had raised with Mr Mandela his walk to freedom from the jail along a dirt road and how he had been a "canny politician" inviting his jailer to his inauguration and bringing white opposition parties into his government.

"Tell me the truth: when you were walking down the road that last time didn't you hate them," Mr Clinton said he questioned Mr Mandela.

"He said briefly: 'I did. I am old enough to tell the truth.' He said: 'I felt hatred and fear but I said to myself, if you hate them when you get in that car you will still be their prisoner. I wanted to be free and so I let it go.'

"He said: 'People can take everything from you. I lost my family, the chance to see my children grow up, the best years of my life. They can take everything except your mind and your heart. those things I decided not to give away. He looked at me and smiled and said: Neither should you.

"That is a lesson that every human being on earth had better learn sooner or later. The grace of it embraces every friend that he had."

Mr Ban said the world is united in praying for Mr Mandela in hospital.

"We are united in concern. We are also joined in admiration for a towering figure in the worldwide fight for equality and justice," the UN Secretary-General told the ceremony.