JOHANNESBURG (AP) — Former U.S. President Barack Obama is set to make his highest-profile speech since leaving office, urging people around the world to respect human rights and other values under threat in an address marking the 100th anniversary of anti-apartheid leader Nelson Mandela's birth.

Obama's speech Tuesday in South Africa is expected to rally people to keep alive the ideas that Mandela worked for including democracy, diversity and good education for all.

While not directly mentioning his successor, President Donald Trump, Obama's speech is expected to be a rebuke to many of Trump's policies.

An estimated 14,000 people are gathering at a cricket stadium for the speech, which will be streamed online.

South African President Cyril Ramaphosa and Mandela's widow Graca Machel will introduce Obama for the annual Nelson Mandela Lecture.