The negotiations will also involve leaders from the Sudan People's Liberation Movement (SPLM), still an NDA member after the January peace deal that ended 21 years of a bloody civil war with the government.
"The negotiations will cover the standing issues which have not yet been resolved with the government," said Sayyed, explaining that they "include power-sharing and the status of our armed forces."
Sudan's ruling National Congress and the SPLM have insisted on applying general power-sharing quotas agreed on in the peace accord, which give them 52 percent and 28 percent of the seats respectively, leaving other parties with a paltry 20 percent and no power to block decisions.
"The share accorded to the other political parties is very small and should be increased," said Sayyed. "The government and SPLM are therefore required to make concessions so that the NDA can participate in the transitional government."
The government delegation, led by Federal Rule Minister Nafie Ali Nafie, will also leave for Cairo on Sunday.
"We are traveling to Cairo to reach a final agreement with the NDA," Information Minister Abdel Basit Sabdarat told reporters. "There is no obstacle preventing this agreement."
The secretary general of the National Congress predicted a week ago that no more than five days were needed to seal a final agreement.
Besides the SPLM, the main movement under the NDA umbrella is the Democratic Unionist party (DUP).
Umma and DUP are both larger than the ruling party and represent Sudan's most powerful religious brotherhoods: the Mahdiya, which has strong support in the strife-torn Darfur region, and the Khatemya, which is closer to Egypt and has its grassroots support in the north.
However, the accord which is due to be reached in the coming days will not be binding on certain NDA members such as the Darfur-based Sudan Liberation Movement (SLM) and the Eastern Front, comprising the Beja Congress and the Free Lions Movement.