US President George W Bush has pledged to work towards bringing stability across Africa, on the second leg of his five-day tour of the continent.
Bush and Mbeki emphasised their points of agreement
Speaking in South Africa after talks with President Thabo Mbeki, Mr Bush said his administration would help resolve Africa's crises, from the civil war in Liberia to the Aids epidemic in southern Africa.
He also praised South Africa, which he called a "force for freedom, stability and progress".
In their joint news conference, the two leaders played down their differences over the crisis in Zimbabwe, with Mr Bush saying he and Mr Mbeki shared the same aims.
On Liberia, the US president reaffirmed both his support for last month's ceasefire agreement and his message to Liberian leader Charles Taylor.
America is willing to put up the resources in the fight (against Aids)
"President Taylor needs to leave Liberia so that his country can be spared further grief and bloodshed," Mr Bush said.
Mr Bush and Mr Mbeki also addressed the turmoil in Zimbabwe, where the opposition is waging a campaign aimed at forcing President Mugabe from power amid a deepening economic crisis.
President Mbeki called on both sides to resolve their differences through dialogue.
The BBC's Barnaby Phillips in Pretoria says the two leaders have different approaches on the Zimbabwe crisis - but in their joint appearance they were very diplomatic.
President Bush said that he and his South African counterpart shared the same objectives and that he trusted President Mbeki to be an "honest broker".
President Bush highlighted the fight against Aids.
He praised efforts to tackle the disease in South Africa, which has the largest HIV-infected population in the world.
Mr Bush reiterated his pledge to spend $15bn on fighting the disease over the next five years throughout the continent.
"America is willing to put up the resources in the fight," he said.
During his stay in South Africa, Mr Bush will not be meeting former president Nelson Mandela - one the harshest opponents of the US-led invasion of Iraq, who described President Bush as a man who "can't think properly".
Kenya's President Mwai Kibaki is also skipping a meeting with President Bush in Uganda on Friday, instead leaving for Mozambique on Wednesday, ahead of a summit of leaders of the African Union.
Mr Bush began his tour on Tuesday in Senegal, where he visited a former slave station and denounced the transatlantic slave trade as "one of the greatest crimes of history".
Mr Bush came close to an outright apology for slavery, which one of his senior advisers called America's birth defect.