The second phase of an UN-led intra-Sudanese political dialogue is scheduled to begin on Tuesday amid divisions among the country's political parties over their participation.
Several parties said they will boycott the talks aimed at resolving the political crisis that followed the 25 October military coup.
The UN, the African Union and the Intergovernmental Authority on Development bloc are seeking to mediate between the military, pro-democracy activists and opposition parties.
The US has urged all Sudanese civilian and military actors to utilise the process to achieve democratic progress and national stability while supporting the UN-led talks.