Former South African leader Nelson Mandela will attend the World Cup opening ceremony despite his increasing frailty, his grandson has confirmed.

Madiba, as he is affectionately known to his countrymen, will appear at the beginning of Friday afternoon's event to greet fans but is likely to retire shortly afterwards, Nkosi Zwelivelile Mandela said.

The news follows intense speculation about whether the 91-year-old Nobel prize winner would play a part in South Africa's proudest moment.

He had a key role in its successful bid to host the games and many had hoped he might do for Bafana Bafana's chances what he did for the victorious Springboks in the 1995 Rugby World Cup – as portrayed recently in the Clint Eastwood film Invictus. However, his public appearances have become increasingly rare – the last was in February on the 20th anniversary of his release from prison - and reports of his increased frailty had led to fears that he may not attend.

Last week, sports minister Makhenkesi Stofile said the former premier had requested four tickets for the opening ceremony – which is followed by the first World Cup match between South Africa and Mexico - as well as the final on July 11.

But he was slapped down by Nkosi Zwelivelile Mandela, the oldest son of Mandela's oldest son and viewed by most as his heir, who said Madiba should not be expected to stand in the cold at his age.

At the weekend, the republic's President Jacob Zuma moved to quell questions, saying that the decision whether to attend was Mr Mandela's alone and may not be made until the day itself.

"If he did not appear, we would understand. If he is there, it will be a bonus for this tournament," he said.

"He will come and greet the fans ... before he retires to his home," Nkosi Zwelivelile Mandela said yesterday. "We're trying to see how long he will stay at the stadium. At least 10 to 15 minutes."