By David Loyn BBC international development correspondent

President Bush says he has a heartfelt commitment to Africa

Six years ago President Bush stunned a major international summit on aid finance by offering far more money to the poorest countries in the world than most people had expected.

It was six months after 9/11 and in his speech outlining US spending plans, he made the link explicit: "We fight against poverty because hope is an answer to terror."

But that was only the first motivation for the aid increase in a list that included a strong moral sense that this was the right thing to do - a theme he returned to in a BBC interview on the eve of what is likely to be his last African visit as president.

"I've got a firm, heartfelt commitment to the continent of Africa and have ever since I became president," Mr Bush said.

The Monterrey Summit in 2002 kicked off a period of more professionalism and seriousness of purpose in development spending - particularly for Africa.

Aids programme

But despite big gestures from Washington and spending that has dwarfed funds from any other country, there are still serious questions over whether the US has delivered on its promises.

The main concern is on the focus on HIV/Aids projects that promote sexual abstinence, and deny funds to groups who try to help commercial sex workers.

PRESIDENT BUSH'S ITINERARY Benin - Cotonou: arrival ceremony, meets president Tanzania - Dar-es-Salaam: meets president, tours hospital; Arusha: tours hospital, textile mill and girls' school Rwanda - Kigali: meets president, visits genocide memorial Ghana - Accra: meets president, state dinner Liberia - Monrovia: meets president, visits university Bush in Africa: Your views

In his five-nation African tour President Bush will visit programmes funded by PEPFAR, his personal anti-Aids initiative that gives money only to groups that follow strict US moral conditions.

The US emphasis on abstinence and trying to encourage people to remain loyal to one partner does strike a chord in traditional African societies, but despite its popularity among church groups, and the billions of dollars promised, the evidence suggests that it does not save lives.

Research, such as a study recently published in the British Medical Journal, has found no evidence of a decrease in infection in abstinence programmes.

The study, among Americans aged 18-21, said that "none of the programmes made any significant difference in preventing pregnancy, reducing unprotected sex, or delaying sexual initiation".

US money is making a huge difference though to those already infected by providing anti-retroviral drugs to more than a million people.

Hard power

In his BBC interview President Bush said there was another key element in the trip. As well as being "a mission of mercy", it is a mission that recognises the "cold realism of the world in which we live".

Africa is seen by the Bush White House as a key front line in their battle against Islamist extremism.

President Bush visited Africa in 2003

They have been wary of direct military involvement since the chaos of the retreat from Somalia after the "Blackhawk Down" incident in 1993.

But the US has given the green light to Ethiopia's military intervention in Somalia, and strung out across the Sahara region there are aid programmes funded by not by USAID, the aid arm of the government, but the Department of Defense.

Thousands of US troops are now permanently stationed in the tiny former French colony of Djibouti on the coast of the Horn of Africa.

Among the decisions President Bush may make on this visit is where to site a new command HQ for the US military on the continent.

Many Africans countries are wary of this. Liberia, which has historic links to the US, is the only country to have offered to host it.

Darfur crisis

The decision by the film director Stephen Spielberg to back out of involvement in the Beijing Olympics will push Darfur further up the agenda of the president's trip than it might have been.

Chinese industrial and economic development is now perhaps the most significant single event across Africa, but in Sudan at least it does not go hand-in-hand with any concern about human rights.