Mr Bush evoked Rwanda's 1994 genocide as he gave his Darfur plea

Mr Bush was speaking in Rwanda - where some 800,000 people were massacred in 1994 - on the third leg of a five-country tour of Africa.

Mr Bush has been making pledges to help fight Aids and malaria, and promises of aid and investment, as he tours Africa.

He is now in Ghana ahead of the final destination on his trip, Liberia.

'Confront evil'

On his visit to Rwanda, Mr Bush drew parallels between the 1994 genocide in Rwanda, and the violence in Darfur - where at least 200,000 people are feared to have died since 2003, and which the president has also termed "genocide".

Mr Bush said he was shaken by his memorial visit

"Evil must be confronted," he said after touring the Kigali memorial.

He said the UN's response to the crisis in Darfur "seems very bureaucratic to me, particularly with people suffering".

Mr Bush pledged an additional $100m (�51m) towards peacekeeping in Darfur but defended his decision not to contribute US troops.

"I made a decision and I stand by it," he said.

"I'm comfortable with the decision I made; I'm not comfortable with how quick the [international] response has been."

Investment and aid

Mr Bush said other nations should "help us get this problem solved once and for all".

PRESIDENT BUSH'S ITINERARY Benin, Tanzania, Rwanda, Ghana, Liberia

Mr Bush toured a memorial to Rwanda's genocide, where he said his emotions had been shaken "to their foundation".

He signed a bilateral investment treaty with Rwandan President Paul Kagame, before flying to Ghana where he was met late on Tuesday by President John Kufuor.

Mr Kufuor said relations with Washington had never been better.

Under a 2006 deal, Ghana is receiving $547m in funds under the Millennium Challenge Corporation, a US initiative which twins aid to fight poverty with so-called "good governance".

Refusal

Mr Bush has been visiting programmes against Aids and malaria

But Mr Bush was not likely to see much evidence of the poverty in Ghana on this trip, says the BBC's Will Ross in the capital, Accra - choosing instead to visit one of its most expensive private schools.

Despite the warm words, Ghana is refusing to host any US facility or base on its territory under the new US military command for Africa (Africom).