New Delhi, March 20 -- Nicholas Haysom, a white South African anti-apartheid activist who was tapped by prisoner-turned-president Nelson Mandela to help draft the country's new constitution that enshrined equal rights for Black people, minorities and white people, has died at 73.

Haysom went on from high-level positions promoting human rights in his home country to a distinguished career as a U.N. diplomat, serving in hot spots from Afghanistan and Iraq to Somalia and South Sudan.

His daughter, Rebecca Haysom, told The Associated Press that he died Tuesday in New York "after a long, valiant battle with heart and lung complications."

U.N. Secretary-General Antonio Guterres said Haysom "devoted his life to justice, dialogue, and reconcil...