Sen. Barack Obama started a two-week tour of Africa on Sunday with a visit to Nelson Mandela's former prison island, paying tribute to the "incredible courage, resilience and hopefulness" of the anti-apartheid movement.

The only black member of the U.S. Senate and one of the Democratic Party's rising stars, Obama said the two-hour visit to Robben Island made him realize that everyday worries in the United States were "fairly trivial stuff compared to the very elemental, basic struggle" of Mandela and other former inmates.

Obama's late father was a goat herder who went on to become a Harvard-educated government economist for his native Kenya.

The senator was guided around the island by Ahmed Kathrada, who was sentenced to life imprisonment in 1964 with Mandela and other leaders of the resistance to white racist rule.

Kathrada was classified as Indian which — according to apartheid's laws — made him superior to black South Africans. He was allowed to wear long trousers and socks and got bigger helpings of food.

Mandela, Sisulu and all the black detainees suffered the humiliation of wearing shorts and petty discrimination like not being allowed syrup or jam at breakfast, he said.

"It is a reminder of the extraordinary struggle that not only Mandela went through but people all over the world go through to obtain things that we take for granted," said Obama. "To stand in Mandela's cell and have a sense of the incredible courage, resilience and hopefulness of these men puts into perspective the work we do back home."

Obama said hopes his trip, which will include a trip to his father's home in Kenya, along with visits to Congo and Chad, will help improve ties between the United States and the continent, and give him a better perspective on problems such as HIV/AIDS.

He is due to visit AIDS patients and meet activists in the impoverished township of Khayelitsha on Monday.