Michelle Obama to meet top women

US first lady Michelle Obama arrived in South Africa last night in what officials have billed as her first major overseas trip.

Obama's visit to South Africa and Botswana started when she arrived at Waterkloof air force base in Pretoria.

It is expected that she will focus on young women leaders and the legacy of the anti-apartheid struggle during her trip.

Obama is travelling with her daughters, Malia and Sasha, and her mother, Marian Robinson, but without her husband, US President Barack Obama.

She left Washington yesterday morning.

Obama is scheduled to meet President Jacob Zuma's wife Nompumelelo Ntuli-Zuma in Pretoria today, before she heads for Johannesburg to visit the Nelson Mandela Foundation, where she will be shown around by Graca Machel, wife of Nelson Mandela.

Later in the afternoon, Obama will visit a daycare centre in Johannesburg, and tour the Apartheid Museum, which chronicles the history of the struggle against white-minority rule.

The six-day trip will also take the first lady to Cape Town and the Botswana capital, Gaborone.

Obama has a packed schedule that includes a safari in Botswana, a visit to Nobel peace prize winner retired archbishop Desmond Tutu in Cape Town, and a trip to the memorial for Hector Pieterson, killed during the anti-apartheid Soweto uprising in 1976.

She will make the keynote speech at a conference of the Young African Women Leaders' Forum, a two-day meeting of 75 women aged 16 to 30 who have leadership roles across the continent.

The visit is Obama's second to sub-Saharan Africa. She last visited the region after a 24-hour stop in Ghana with her husband in 2009.

This is her first solo trip to the continent.

The US State Department described the visit as a mix of policy and personal pilgrimage.

"She's coming on this trip to talk about women's development and youth development, and South Africa's a leader in that, not only on the continent but globally," said Elizabeth Trudeau, spokesman for the US embassy in Pretoria.

"A visit to South Africa is important for them as a family. She'll be visiting many struggle-era landmarks."

The White House has emphasised the importance to the US first family of South Africa's anti-apartheid movement, which President Obama has described as the first political cause he adopted.

Trudeau said the White House considers this to be Michelle Obama's "first major overseas trip".

She made her first solo trip as first lady last year, stopping briefly in Haiti before going to Mexico for three days.

Relations between the US and South Africa have suffered a number of diplomatic strains this year.

In March, South Africa allowed exiled Haitian former president Jean-Bertrand Aristide to return home, despite a personal appeal from Barack Obama that he be kept in South Africa until after a presidential run-off election in Haiti that the US feared he would attempt to destabilise.

Zuma has lashed out at the Nato-led bombing campaign in Libya, which Washington supports.