Sadeq al-Magli, the foreign ministry spokesman, did not elaborate, however.
The UN had been pushing for a much larger role in Darfur - where AU peacekeepers are already operating - in an effort to put an end to the fighting.
Conflict in Darfur has claimed more than 200,000 lives and left 2.5 million displaced.
The Khartoum government has a long-standing opposition to the deployment of 20,000 UN troops as proposed by the UN Security Council.
In deference to Khartoum's opposition, the UN scaled back its plans to replace the current AU force of 7,000 troops in Darfur with the much bigger UN operation.
Earlier on Friday, Kofi Annan, the outgoing UN secretary-general, said he was encouraged that Omar al-Bashir, the Sudanese president, will shortly agree to the hybrid AU-UN force, along with a ceasefire and renewed peace efforts.
"I do fervently hope that we are now at last close to rescuing the people of Darfur from their agony," he said. "But after so many disappointments, I take nothing for granted."
Annan made the announcement during his farewell speech to the Security Council. Annan will be replaced by Ban Ki-moon in January.
Al-Bashir had opposed to a council resolution adopted in August that called for more than 20,000 UN peacekeepers to replace the AU force in Darfur.
He had also opposed the deployment of UN troops in a hybrid force, claiming a UN force would compromise Sudan's sovereignty.
In a letter from the UN that Ould Abdallah delivered to al-Bashir, Annan stressed that the UN plan, which culminates with a hybrid African Union-UN force, must be accepted in its entirety.
In the letter, Annan said a ceasefire in Darfur is "imperative" because of the increase in violence in the war-torn region over the last few weeks, including a surge in attacks on civilians by militias.
To achieve a ceasefire, he said, efforts to get all rebel groups and militias to join the Darfur Peace Agreement must be immediately reactivated.
Fighting in Darfur began in February 2003 when rebels from African tribes took up arms in opposition to Sudan's Arab-dominated government.
The government is accused of unleashing Arab tribal militia known as the Janjawid against civilians in a campaign of murder, rape and arson.
The government denies the charge. More than 200,000 people have been killed and 2.5 million displaced by three years of fighting.
|United Nations forces could join African |
Union troops to build a hybrid force
Annan stressed that the tri-phase UN plan to bolster the African Union force was agreed to in Addis Ababa, Ethiopia on November 16 by the 53-nation African body and the international community.
He said it was later endorsed at a November 30 summit of the AU's
eace and security council - which includes Sudan.
"The unequivocal commitment of all stakeholders to these measures and the active support of your government would be essential to take forward and secure comprehensive United Nations funding for the three phases, which should be seen as a continuum," Annan wrote.
Annan wrote to al-Bashir that UN personnel and equipment in the first phase "must be deployed without delay".
A second, larger support package would include the deployment of several hundred UN military, police and civilian personnel to the AU mission along with aviation and logistical assets.
Annan told the Sudanese president that every effort would be made to find African troops for the UN force but it will use "a broader pool of troop contributing countries" if necessary.
The third phase would be the AU-UN hybrid operation, with the two organisations jointly appointing a special envoy to lead it and the military commanders, and UN involvement in its command and control structure.