The 15-nation Security Council came to Addis Ababa, seat of the African Union, to consult AU officials before returning to Sudan where it is trying to persuade the government to accept UN peacekeepers by the end of the year.
The under-financed and ill-equipped African Union has 7,000 troops and monitors in Darfur, who are the only bulwark against atrocities in the region where ethnic cleansing has driven 2 million people from their homes.
"Before the UN actually takes over the African Mission in Sudan (AMIS) needs to be reinforced and we will be working together to make sure AMIS is reinforced," Emyr Jones Parry, Britain's UN ambassador, said after ambassadors met Alpha Oumar Konare, chief executive of the 53-nation AU.
According to a council member at the meeting, Konare expected more troops from Ghana, Rwanda and Nigeria to make a total of 10,000 soldiers and observers in Darfur.
He also wants back-up support, such as transport and communications, from Western nations and on Wednesday said he wrote a letter to Nato outlining AU needs, the envoys reported.
But Konare stressed he did not want Western soldiers on the ground, which Sudanese officials regard as invaders.
Sudan signed a peace agreement with the main Darfur rebel group on May 5, but two other rebel factions refused to sign, further adding to mayhem that has cost at least 200,000 lives from fighting, hunger and disease.
Konare and Jones Parry told reporters the African Union and the United Nations were on the same track over the future of a UN Darfur force, which is expected to happen by the end of the year, providing Sudan gives its consent.
"We mapped out between us what we would like to see happen," Jones Parry said. "At the request of the African Union, the United Nations is prepared to take over the peacekeeping operation.
Konare told reporters he was "confident" that this would happen, adding: "The troops are not coming to start a war with Sudan."
Sudan, which is an AU member, has agreed to a military planning team comprising UN and AU officials. Jean-Marie Guehenno, head of UN peacekeeping, began his mission at AU headquarters on Wednesday before heading to Sudan.
The fighting in Darfur escalated in early 2003 between African rebel farmers and Arab tribesmen, armed by the government and blamed for many of the atrocities, including widespread rape.