Sudan has categorically rejected a statement by US Secretary of State Colin Powell in which he described the killings in Darfur as genocide.
Darfur refugees say their villages are bombed and then raided by militias
Foreign Minister Mustafa Osman Ismail said the US was using a humanitarian problem for its own political purposes.
And Foreign Affairs Minister Najib Abdul Wahab told the BBC the government had made mistakes, "but the situation is not tantamount to genocide".
The US is seeking a new UN resolution that threatens Sudan with sanctions.
The resolution also calls for more African Union monitors to go to the western region.
Mustafa Osman Ismail said the US was "isolated" in its use of such strong language, which he said was aimed at winning African-American votes in November's election.
In South Darfur, tens of thousands of people have fled renewed violence in the past two weeks, reports the aid agency Oxfam.
'Pattern of violence'
Up to 50,000 people may have died and a million have been made homeless during the conflict in Darfur between government forces and rebel groups, which broke out last year.
More than 1m displaced
Up to 50,000 killed
More at risk from disease and starvation
Arab militias accused of ethnic cleansing
Sudan blames rebels for starting conflict
Washington says Khartoum is failing to prevent atrocities against civilians by the pro-government Janjaweed Arab militia.
Its call for more monitors won widespread support at Thursday's meeting of the UN Security Council, but China, Pakistan and Algeria expressed reservations about the need for sanctions.
Mr Powell based his verdict that genocide was occurring in Darfur on interviews with more than 1,800 refugees who had fled Darfur into neighbouring Chad.
He told the US Senate Foreign Relations Committee: "We concluded that genocide has been committed in Darfur, and that the government of Sudan and the Janjaweed bear responsibility and genocide may still be occurring."
The testimonies, collected by US State Department investigators, showed a pattern of violence which was co-ordinated, not random, Mr Powell said.
Mr Ismail said the US was using Darfur to try and deflect international attention from its problems in Iraq.
"They should not use a humanitarian problem for political agenda," he said during a visit to South Korea.
Meanwhile, Foreign Affairs Minister Najib Abdul Wahab told the BBC that neither the European Union nor the African Union had used such strong language.
More than a million people have fled their homes
He described the conflict as a serious confrontation between farmers and cattle breeders, which he said the government had been unable to handle because Darfur's infrastructure was weakened by rebel groups.
A Sudanese parliamentary delegation has accused the US of leading a global hate campaign against the Sudanese government.
The deputy parliamentary speaker, Angelo Beda, accused Washington of behaving like a "bull in a china shop".
He said US pressure over Darfur could threaten a peace agreement to end the long-running north-south civil war - a separate conflict.
The US would like the Security Council to vote on its new draft resolution next week.
The proposed resolution says Sudan has failed to fully comply with a previous UN resolution which was passed in July. It gives the government a new 30-day deadline.
If Khartoum does still not comply, sanctions may be introduced "including with regard to the petroleum sector". Sudan currently produces about 320,000 barrels of oil per day.
The resolution also calls for:
BBC state department correspondent Jill McGivering says the use of the word genocide does not legally oblige the US to act, but it does increase the moral and political pressure.
- the expansion of the number and mandate of the current 300 African Union troops in the country
- international overflights in Darfur to monitor what is happening, and an end to Sudanese military flights there
- UN Secretary General Kofi Annan to assess whether acts of genocide have been carried out and identify the perpetrators.
Ten years ago, the UN was heavily criticised for failing to stop genocide in Rwanda.