Jan Pronk, the UN special envoy, and Ahmed Salim Ahmed, the special AU envoy on Sudan, arrived on Saturday and were to hold a series of meetings with all parties in the crisis to ensure the Sunday deadline is adhered to by all.
The peace talks in Abuja coincide with the visit by Louise Arbour, the UN high commissioner for human rights, who is in Sudan to press the government to end rights abuses, particularly in its suppression of a three-year uprising in Darfur.
UN officials said Arbour was due to meet with senior officials from the Sudanese government in Khartoum before travelling to Juba to hold talks with members of the south Sudan government during her week-long visit.
Her trip will also include visits to South and West Darfur state capitals of Nyala and el-Geneina, where she will meet with governors of both states as well as local leaders, women's groups and nongovernmental organisations.
Ready to sign
The Sudanese government said on Saturday it was ready to sign the AU-brokered deal despite reservations over some of its contents.
But the divided Darfur rebel movements voiced reservations about the peace accord, which they are negotiating at talks in Nigeria with the Khartoum goverment.
"The government is prepared to sign the (AU) document even with our reservations. Our reservations are important but they are not as important as to spoil the peace process," a spokesman for the Khartoum delegation said in Abuja.
Sudan's rulers say they are ready
to sign the AU-brokered deal
"The top priority for the government of Sudan is peace and stability," spokesman Abdulahman Zuma added.
"We also want the AU to claim victory over this crisis. We do not want to let the AU down and that is why we have given a lot of concessions in all aspects of this peace process," he said.
"We appeal to all parties to exert the utmost degree of concession and to show that we are capable of resolving the reservations we have about the AU document."
But Ahmed Hussain, spokesman for one of the Darfur rebel groups, the Justice and Equality Movement (JEM), said his side wanted prior guarantees from the international community that the peace deal would be enforced.
"Before we sign the agreement, we need a clear guarantee from the African Union and the international community that the contents of the peace pact will be respected by all the parties to the conflict," he said.
"This is our major reservation about the agreement. We want to be sure of the implementation and the mechanisms for it.
Sudan has been wracked by
unrest and civil war for years
"The movements believe that when dealing with the government in Khartoum we need all the assurance that we can get.
Hussain continued: "But the AU does not seem to understand our point of view.
"We want these our reservations to be inserted in the AU peace document before we sign it."
The rebel movements are also insisting on having the Arabic translation of the AU document to ensure that the contents are similar "legally and administratively" to those of the English version, Hussain said.
Last week, the UN Security Council and Washington imposed a travel ban and economic sanctions on four Sudanese blamed for bloodshed and rights abuses in Darfur, including rebel, government and allied militia leaders.
Up to 300,000 people have died and 2.4 million more been displaced in three years of fighting between rebels and Khartoum-backed militias in Darfur.