Sudan's President Omar al-Bashir threatened to call off the talks in Qatar and return negotiations to Sudan if agreement was not reached by Thursday, and he carried out his threat.
Chief government negotiator Ghazi Salaheddine says the Sudanese delegation will leave for Khartoum on Friday.
Ahmed Hussain Adam, a rebel spokesman, described the move as "a declaration of war" in remarks to Al-Jazeera TV.
Last minute disagreements foiled a goal to reach an accord by the end of the year.
The talks were also marred by renewed clashes between government and rebel forces. Thousands were displaced during the new fighting.