"This is just another sort of pressure brought against the government of Sudan by the United States and Western governments, the kind of general political pressure that shows the US is not a friend of Sudan," said Ahmad Hassan al-Zubair, Sudan's finance minister.
"We will prove that it is true that the conflict in Sudan is an internal tribal problem and it will be for the national government to solve this problem," he said on leaving an African Union summit in Burkina Faso on Thursday.
However, a spokesman for the rebel Sudan Liberation Movement (SLM), Abd al-Hafiz Mustafa Musa, hailed the US move as "a welcome development".
Earlier, US Secretary of State Colin Powell told a Senate hearing that evidence compiled by the US and other sources "concluded that genocide has been committed in Darfur and the government of Sudan and the Janjawid bear responsibility".
But African Union chief Alpha Oumar Konare noted at the Burkina Faso summit that during Powell's visit to the west of Sudan in late June, the US secretary of state stressed that the crisis was not genocide.
"If today he is affirming that there was genocide, we would also like to be privy to such information," Konare said.
The presidents of Sudan and neighbour Chad, which has received thousands of refugees fleeing Darfur over the last several months, attended the summit aimed at finding remedies to the chronic unemployment problem facing Africa.
They held discussions on the margins of the two-day event, which Konare said showed the willingness of all actors in the Darfur crisis to find a peaceful, diplomatic solution.
"A military solution will not resolve the problems in Darfur and would be an absolute catastrophe," he said, adding that the Sudan government has supported the reinforcement of the current African Union mission in Darfur.
"The African Union does not support any intervention by a non-African force in the Sudan issue," he added.