The Sudanese army bombed bases of the Rapid Support Forces, claiming that they weren't abiding by the ceasefire.
The truce brought some reduction in fighting and gave space for limited humanitarian relief, but has been marred by clashes and air strikes.
Witnesses reported columns of black smoke rising to the west of central Khartoum and shelling near an army camp in southern Khartoum.
Fighting has driven 1.1 million from their homes, with a truce that was designed to allow for the delivery of aid.
The breakthrough in Sudan is important because it shows how Saudi Arabia and the US can work together to bring peace to the region.
The new agreement calls for a seven-day ceasefire to begin 48 hours after signing. Numerous previous ceasefire agreements were violated.
Can they move from pushing for stability in Syria to creating real stability in Sudan? Is the region entering a new diplomatic era?