Updated

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 on 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 were 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.

This is Obama's first visit to Africa since leaving office in early 2017. He stopped earlier this week in Kenya, where he visited the rural birthplace of his late father.

Obama's Mandela speech is expected to highlight how the Nobel Peace Prize winner, who was imprisoned for 27 years, kept up his campaign against what appeared to be insurmountable odds to end apartheid, South Africa's harsh system of white minority rule.

Mandela, who was released from prison in 1990 and became South Africa's first black president four years later, died in 2013, leaving a powerful legacy of reconciliation and diversity along with a resistance to inequality, economic and otherwise.

Obama has shied away from public comment on Trump, whose administration has reversed or attacked notable achievements of his predecessor. The U.S. under Trump has withdrawn from the 2015 Paris climate agreement and the Iran nuclear deal while trying to undercut the Affordable Care Act or "Obamacare."

Instead of commenting on politics, Obama's speech is expected to draw on broader themes and his admiration for Mandela, whom America's first black president saw as a mentor.

When Obama was a U.S. senator he had his picture taken with the newly freed Mandela. After Obama became president he sent a copy of the photo to Mandela, who kept it in his office. Obama also made a point of visiting Mandela's prison cell and gave a moving eulogy at Mandela's memorial service in 2013, saying the South African leader's life had inspired him.

___

Follow Africa news at https://twitter.com/AP_Africa