Sudan has been under a state of emergency since 1999, a measure which allows the government to detain people without charge. The government promised to end emergency law after a peace deal signed in January to end a civil war in the south.
Al-Turabi, a former ally of President Umar Hasan al-Bashir, was jailed last September after the government accused his party of attempting a coup and of involvement in a separate rebellion in Sudan's western Darfur region, which started two years ago.
Foreign Relations Minister Mustafa Usman Ismail told the pan-Arab daily Al-Sharq Al-Awsat that Sudan would release al-Turabi and all political prisoners as emergency laws were lifted.
"Now we are moving to a stage in which we will lift the state of emergency and not use any exceptional laws. When we reach this stage then Dr al-Turabi, certainly, and all those remaining will be released," he said.
Rights activists say there are hundreds of political prisoners, though they do not have exact figures.
Asked when he expected al-Turabi would be released, Ismail said: "Soon, in my view. It will not be a long time before you see Dr al-Turabi released and free to practice his political life.
"We are moving towards emptying the prisons completely of any political detainees."
The government promised to end
Several members of al-Turabi's Popular Congress party, which was suspended in April last year, were released in January.
Since his split with al-Bashir's government, al-Turabi has spent much of his time in jail or under house arrest.
Despite the government's commitment under the southern peace deal to end emergency laws, some analysts say Khartoum could keep them in place in certain areas of the country, such as Darfur and in the east, where the military wing of the opposition Beja Congress has carried out minor operations.
In February, the group called for more power and resources for the impoverished region, a common rebel demand in the vast country.
"We are ready for dialogue with the rebels of the east. The vision of the government is very clear, it is that the government seeks eventually a comprehensive peace in all areas of Sudan without excluding anyone," Ismail said.