The US's first black President Barack Obama will deliver the annual Nelson Mandela lecture in South Africa's main city, Johannesburg, on 17 July to honour the centennial of the anti-apartheid icon's birth, the Nelson Mandela Foundation has said.

The foundation's chief executive, Sello Hatang, said the foundation had been looking for someone with "an Africa heritage" to deliver the address.

"We thought who can [better] represent the legacy of Madiba than the person who we believe took on the baton when he became president of his own country," Mr Hatang said, referring to Mr Mandela by his clan name.

The lecture will focus on "creating conditions for bridging divides, working across ideological lines, and resisting oppression and inequality", the foundation added ina statement.

Mr Hatang told AFP news agency that Mr Mandela was "elated" when Mr Obama was elected in 2008 "because he saw it as a moment in American history".

"We hope that it will again be a significant moment for the two legacies to join," he said.

Mr Mandela became South Africa's first black president following the end of the racist system of apartheid in 1994.

He spent 27 years in prison for fighting for the freedom of black people.

Mr Mandela died in 2013 at the age of 95.