U.S. armed forces would not be overstretched even if American troops were to join a peacekeeping force in Liberia, President Bush said Wednesday on the second day of his five-nation African tour.

American involvement in West Africa seemed all but certain Wednesday.  When asked by South African President Thabo Mbeki (search) if the U.S. planned to play a role in ending the Liberian crisis, Bush told reporters he answered affirmatively.

"I said, 'Yes, we'll be involved, and we're now discussing the extent of our involvement,'" Bush told reporters during a joint news conference with Mbeki.

Liberia's civil war has dragged on for years and the country's instability has contributed to other conflicts in neighboring Guinea (search), Sierra Leone (search) and Ivory Coast (search). 

Bush has pressed for Liberian President Charles Taylor (search), widely seen as the instigator of the region's troubles, to step down, but Taylor, recently indicted for war crimes in Sierra Leone, has stalled on his promise to do so.

The United States already has tens of thousands of soldiers in Iraq, Afghanistan and Kosovo. Bush said that whatever he decided to do about Liberia, "we won't overextend our troops."

Mbeki said that the military burden in Liberia peacekeeping "really ought to principally fall on us as Africans."

Britain and France recently ended the civil wars in their respective former colonies of Sierra Leone and Ivory Coast with the dispatch of hundreds of peacekeeping troops, and would like the U.S. to do the same with Liberia, which was founded by freed American slaves in 1847.

The United States has trained battalions of African troops, Bush said, and "helping people help themselves" was one method of ensuring the U.S. military would not become stretched too thin there.

"It's in our interest that we continue that strategy so that we don't get overextended," Bush said.

Bush did not say whether he will deploy troops to Liberia. He promised that "we will work closely with the United Nations and the Economic Community of West African States (search) to enforce the cease-fire, to see to it that Mr. Taylor leaves office so there can be a peaceful transition in Liberia."

Bush also wants African leaders to put more pressure on President Robert Mugabe (search) of Zimbabwe to step down and hold new elections. Mbeki, whose African National Congress party has longstanding ties to Zimbabwe, has insisted that he will not pressure Mugabe.

About half of Zimbabwe's population faces starvation. Dozens have been killed in state-orchestrated political violence. Thousands more have been beaten, jailed, raped or tortured for their views.

Diplomatic efforts led by Britain, Zimbabwe's former colonial power, to force Mugabe out peacefully have failed.

Wednesday, Bush backed Mbeki's efforts in Zimbabwe.

"The president is the one who is most involved" in mediating troubles in Zimbabwe," Bush said. He believes he's making good progress. ... I don't have any intention of second-guessing his tactics."

In the matter of AIDS, South Africa has the highest number of infections on the continent — 5 million. It also is one of 14 hardest-hit African and Caribbean countries that would benefit under Bush's proposed five-year, $15 billion AIDS initiative.

"South Africa recently increased its budget [for AIDS]. We noticed and we appreciate that," Bush said. "People across Africa have the will to fight this disease, but often not the resources, and the United States is willing to put up the resources to help win the fight. "

On his five-nation tour of Africa, Bush is spending the most time in South Africa, the place where the "apartheid" system of white-minority rule kept non-whites disenfranchised for the second half of the 20th century.

"Your nation's recent history is a great story of courage and persistence and the pursuit of justice," Bush said. "This is a country that threw off oppression and is now the force of freedom and stability, and a force for progress, throughout the continent of Africa."

Absent from Bush's schedule is any appearance or meeting with Nelson Mandela, who preceded Mbeki as South Africa's president.

Mandela, the popular leader and hero of the anti-apartheid movement, has been a harsh and outspoken critic of Bush for leading the war against Iraq without support from the United Nations.

Administration officials have said Bush's time was being reserved for current African heads of state. Mandela was expected to be out of the country for the Bush visit.

Dozens of South Africans protested this week outside the U.S. Embassy here and the consulates in Johannesburg and Cape Town. Protests by political parties, trade unions and other groups were planned during Bush's stay in southern Africa, which ends Friday.

Besides resentment over the war, South Africa's generally positive relations with the United States were dealt a blow by the Bush administration's decision to end military aid to 35 countries, including South Africa, that opposed the U.S. demand for immunity for Americans in the International Criminal Court.

Bush's visit to Africa began Tuesday in the Atlantic port city of Dakar, the capital of Senegal. He met privately with Senegalese President Abdoulaye Wade, then with a larger group that included Wade and the heads of seven other West African democracies.

Bush and his party then rode in Wade's presidential yacht to Goree Island for a tour of a centuries-old slave house where hundreds of thousands of Africans were bought and sold.

In a speech on the island, Bush stopped short of issuing the blanket apology for slavery that some civil rights advocates had sought. But he acknowledged that the scars of slavery still sting American society.

"One of the largest migrations in history was also one of the greatest crimes of history," the president said.

The Associated Press contributed to this report.