JOHANNESBURG, South Africa (AP) _ Sen. Barack Obama, the only African-American in the Senate, paid tribute Wednesday to South Africans' fight for freedom, saying they helped inspire his own political career.

With handshakes, hugs and his congenial grin, the Illinois Democrat toured Soweto, the township where white rulers once tried to confine by night the blacks who worked in their homes, offices and mines by day.

Obama arrived in South Africa on Sunday, the first stop on a sentimental tour of the continent of his late father _ a goat herder who went on to become a Harvard-educated government economist for his native Kenya.

The senator also will visit his father's village in Kenya and travel to Djibouti and Chad on a trip he hopes will bring new light to Africa's importance.

Aides said Wednesday that Obama had scrapped plans to visit Congo and Rwanda at the request of the U.S. Embassy in Congo because of post-election fighting in that country's capital, Kinshasa.

Obama began his tour Sunday with a visit to Nelson Mandela's former prison at Robben Island. He has met with black businessmen, AIDS victims and U.S. Embassy officials, among others.

His visit to South Africa coincided with one by Oprah Winfrey, who was there to interview candidates for her Oprah Winfrey Leadership Academy for Girls-South Africa, which is opening in January 2007, according to her company, Harpo Inc.

The talk show host, who is now back in the United States, had offered Obama a flight to Africa on her private jet, according to a spokeswoman for her company Harpo Inc.

Obama told reporters earlier this week in South Africa that he turned down the ride because he would have to reimburse Winfrey for the flight.

At the Hector Pieterson Museum, built on the site where peaceful child protesters were gunned down by police 30 years ago in an attack that awakened the world to the brutality of the apartheid regime, Obama said he became involved in politics to fight for divestment of U.S. interests in South Africa to protest apartheid.

``If it wasn't for some of the activities that happened here, I might not be involved in politics and might not be doing what I am doing in the United States,'' he said.

He put his arm comfortingly around Antoinette Sithole as she explained an iconic picture of her, running with mouth open in a scream alongside a friend carrying the body of her slain brother, Hector.

``All of us drew inspiration from what happened here, all of us wept when we saw some of the deaths, including Hector's,'' Obama said.

Obama, who was 15 at the time of the 1976 Soweto Uprising that gave renewed impetus to the fight against white rule, said the event also highlighted the importance of young people in politics.

At the U.S.-funded Rosa Parks Memorial Library, set in a community center behind St. Paul's Anglican Church, Obama leaned over desks to chat with visitors.

He promised to introduce 37-year-old documentary filmmaker Themba Nkabinde to producer Spike Lee. Nkabinde told the senator he had just won a scholarship to study at New York University _ Lee's alma mater.

In the upstairs gallery, so packed some people sat on the floor, Obama got down to speak face-to-face with teenagers.

Afterward, one asked ``Who is he?'' When told he was the only black U.S. senator, that his father was an African and that there was talk he might one day be the first black president of the United States, she squealed with excitement, ``Ooooh, let's go and touch him!''

Some American tourists at the museum recognized Obama and rushed to introduce themselves. Jim Lockerbie presented a museum pamphlet for an autograph, saying he had taught world history for 33 years at Newport High School in Seattle and was delighted by the changes since he last visited South Africa in 1971.