Former president Nelson Mandela will not attend the ANC's centenary celebrations in the Mangaung municipality in the Free State at the weekend, the ruling party's secretary general said on Friday.

"I think it would be unreasonable for any South African to expect Tata Mandela to travel from Mthatha [in the Eastern Cape] to Bloemfontein," the ANC's Gwede Mantashe told SABC radio news.

He said he had visited Mandela in his home town - Qunu, in the Eastern Cape - on December 21.

"He is in good spirits but very, very old," said Mantashe.

"The old man is 94. He is not coming and we are not expecting him to come."

Earlier in the week, ANC chair Baleka Mbete told journalists that the party hoped Mandela would be able to be there. She said a total of 46 sitting heads of state had confirmed their attendance for the event.