The Sudan government has signed a preliminary peace agreement with the main opposition umbrella group, the National Democratic Alliance (NDA).
Momentum for peace is growing after the end of 21 years of war in the south
The signing of the accord marks another key step in efforts to bring peace to all of Africa's largest country.
A final deal due to be signed in February should end 16 years of low-intensity conflict, mainly in the north and east of the country.
A peace deal with the southern-based SPLA rebels was signed this month.
Foreign Minister Mustafa Osman Ismail told journalists on Sunday that as part of their strategy they were considering releasing all political prisoners.
The main Islamist opposition leader Hassan al-Turabi is currently in prison.
"We hope no one will remain in Sudanese prisons except criminals and the unjust," he said, in comments quoted by the independent Al-Ayyam newspaper.
The NDA is made up of more than a dozen political, civil, union and professional groups - including the SPLA.
The BBC's Alfred Taban in the capital, Khartoum, says that once the SPLA reached a peace agreement with the government, its NDA allies were bound to follow suit.
The NDA was formed in 1989 in response to the coup in which President Omar al-Bashir seized power.
The deal, signed on Sunday evening in Cairo, represents a framework for a comprehensive political solution between the two sides with the aim of:
- Lifting the state of emergency in place since 1989
- Reintegrating the NDA into Sudan's political life
- Merging rebels back into the army
The major stumbling block to peace across Sudan, remains the conflict between the government and rebels in the western Darfur province which has claimed the lives of an estimated 70,000 people and displaced 2m more.
One of Darfur's rebel groups, JEM, has welcomed the appointment of Vice President Ali Osman Taha as chief negotiator to try to resolve the Darfur crisis.
Taha (left) secured a southern deal after two years of negotiations
They said it meant the issue had been accorded some importance by the government.
In a speech in Khartoum, Mr Taha, who negotiated the southern peace deal on behalf of the government, stressed the government's "total" commitment to a ceasefire on all fronts.