UN chief Kofi Annan has described the situation in Darfur as one of the worst nightmares in recent history.
The Darfur conflict has displaced millions of people
The conflict in the Sudanese region was outrunning efforts to find a solution, he told African Union (AU) leaders at a summit in the Gambian capital, Banjul.
Tens of thousand of people have died in three years of conflict in Darfur, most killed by pro-government militias.
The summit is expected to pressure Sudan to allow UN peacekeepers to take over from the AU later this year.
The AU's mandate in Darfur expires in September, but the Sudanese government has yet to confirm whether it will allow UN troops into the region.
Rival factions in the region signed a partial peace agreement in May, but the situation remains volatile.
In his speech, Mr Annan painted a mixed picture of Africa's progress as a continent.
He praised what he called its inexorable and unstoppable progress on development, but said much remained to be done.
"Overall, the number of Africans living in extreme poverty continues to increase," he said.
"The spread of HIV/Aids continues to outpace our efforts to halt it.
"The conflicts in Darfur, Ivory Coast, Somalia and northern Uganda continue to outrun efforts for a solution.
"Many governments continue to suppress opposition parties and a free press... Many continue to practise or tolerate large-scale corruption."
He called for a fresh strategy to build development, security and human rights.
Somalia, Ivory Coast, and the impending trial of former Liberian President Charles Taylor are also on the agenda at the summit.
Venezuelan President Hugo Chavez and Iranian President Mahmoud Ahmadinejad are also attending the summit as invited guests.
Fifty-two villas and a huge hotel and conference centre have been built in just under six months just outside Banjul, to accommodate the delegates.
Some 200,000 people are thought to have died in Darfur, a vast region in the west of Sudan, in a three-year conflict.
Most have died in attacks by pro-government militias against civilians.
Rebel forces took up arms in February 2003, accusing the government of discriminating against Darfur's black Africans in favour of Arabs.
A partial peace deal was agreed in May, but not all sides signed the agreement and fears have grown over worsening conditions in camps home to displaced people.
The International Criminal Court was set up by the UN in 2002 to prosecute individuals for war crimes, genocide and crimes against humanity.