UN Secretary General Ban Ki-moon has described Sudan's decision to allow 3,000 UN troops into Darfur as "a very positive sign".
The African Union force is struggling to halt the violence
The UN contingent will provide support for 7,000 struggling African Union troops there.
Sudan's apparent change of heart comes after months of international pressure to accept UN peacekeepers.
But Khartoum is yet to agree to the deployment of a much-larger AU force of 20,000 troops proposed by the UN.
The four-year Darfur conflict between rebels and pro-government Arab militia has seen more than 200,000 deaths and at least 2.4 million displaced.
Mr Ban said the UN and the AU would "intend to move quickly to prepare for the deployment of the heavy support package" for the AU troops.
UN DARFUR PLAN
Phase 1 - UN financial backing for AU mission
Phase 2 - UN sends logistical and military support
Phase 3 - UN takes joint command of hybrid force
He was referring to the second phase of a UN plan which envisages that UN attack helicopters and armoured personnel carriers would also be deployed to help the AU troops.
Earlier on Monday, Sudanese Foreign Minister Lam Akol said that Khartoum had fully accepted the second phase of the plan.
British aid agency Oxfam has launched an appeal for humanitarian aid for the Darfur region.
Oxfam says it needs £5m ($10m) to help displaced people in the region who continue to flee from violence.
"This is the greatest concentration of human suffering in the world and an outrage that affronts the world's moral values," Penny Lawrence, Oxfam's international director said after a tour of Darfur.
The international aid agency is currently providing clean water, health and sanitation services to more than 500,000 people in Darfur and eastern Chad.
"Nearly one million people are not getting any aid at all and in some areas the aid effort is under threat due to increasing insecurity," an Oxfam statement said.
Visiting US official John Negroponte had also warned Sudan of isolation if it failed to stop harassment of humanitarian workers and rejected the deployment of UN peacekeepers in the war-torn region.
"The denial of visas and harassment of aid workers has created the impression that the government of Sudan is engaged in a deliberate campaign of intimidation," he said at the end of his tour of Sudan.