United Nations Secretary General Kofi Annan has criticised the developed world for being too slow to respond to the crisis in Sudan's Darfur region.
The US has called the crisis genocide, but the UN has not
"We were slow, hesitant, uncaring," Mr Annan said in a BBC interview.
He said the international community had "learnt nothing from Rwanda" - a reference to the 1994 genocide there.
At least 180,000 have died since 2003 in the western region of Darfur. More than two million people have been forced from their homes.
Human rights groups, the US Congress and the US government say that genocide is taking place.
However, a UN team sent to Sudan to investigate concluded that war crimes had been committed, but there had been no intent to commit genocide by the Sudanese government.
The UN secretary general was heavily criticised at the time of the Rwandan genocide for failing to take heed of warnings from his staff on the ground.
In the case of Darfur, Mr Annan has made a point of continuing to demand international action and his comments in an interview for the BBC's Panorama programme are the strongest yet, says the BBC's Fergal Keane.
Asked by our correspondent whether the judgment on Darfur would be as damning as in the case of Rwanda, Mr Annan replied: "Quite likely".
Darfur has become the first case referred by the UN Security Council to the International Criminal Court.
ICC chief prosecutor Luis Moreno Ocampo told the Security Council on Wednesday that his office had found evidence - including widespread rape and sexual assault - that warranted the bringing of the Darfur case to the court.
He accused the Sudanese authorities of failing to take action against those responsible.
Violence in Darfur has declined in recent months.
Britain's Minister for International Development, Hilary Benn, believes that has much to do with the threat of prosecution by the ICC now hanging over the heads of Sudanese leaders, our correspondent says.
You can see Mr Annan's full interview on the Panorama programme at 2115 GMT on Sunday on BBC One.