JOHANNESBURG (AP) - President Barack Obama opened a day of remembrance and celebration on Tuesday for his personal hero, Mr Nelson Mandela, arriving in South Africa for a memorial service honouring the anti-apartheid icon who died last week at age 95.

Air Force One touched down at a military base near Johannesburg on a rainy morning. Joining Mr Obama on the 16-hour trip from Washington was First Lady Michelle Obama, former president George W. Bush and his wife, Laura, and former secretary of state Hillary Clinton. Former presidents Bill Clinton and Jimmy Carter were also scheduled to attend the memorial service, but travelled to South Africa separately.

The Obamas, the Bushes and Mrs Clinton departed the front steps of the presidential plane together, a rare grouping of a current, former and possibly future president.

Mr Obama will be among the speakers at Tuesday's memorial, joining tens of thousands of South Africans and dozens of dignitaries at the outdoor stadium in Johannesburg. A singing, joyous crowd was filling the stadium early on Tuesday morning despite the rainy conditions.

White House aides said Mr Obama began crafting his 20-minute remarks for the memorial after Mr Mandela's passing last week. The President was expected to discuss Mr Mandela's impact on his own life, as well as his transformation from prisoner to president.

"He obviously is cemented in our memory as an icon, but he was an extraordinary political leader, an extraordinary leader of a movement to bring about change," said Mr Ben Rhodes, Mr Obama's deputy national security adviser.