Britain may not be able to continue evacuating its nationals in Sudan when a ceasefire ends - something due to happen later on Thursday - and they should try to reach British flights out of the country immediately, foreign minister James Cleverly said. "Now is the time to move because when the ceasefire ends, my ability to give the kind of limited assurance I can give now might go and we might not be able to evacuate," Cleverly told Sky News television. Sudan's army and the Rapid Support Forces battled on Khartoum's outskirts on Wednesday, undermining a truce in their 11-day conflict, but the army expressed willingness to extend the ceasefire. The army late on Wednesday said its leader, General Abdel Fattah al-Burhan, gave initial approval to a plan to extend the truce for another 72 hours and send an army envoy to the South Sudan capital, Juba, for talks. The Sudanese armed forces and the RSF previously agreed to a three-day ceasefire that was due to expire late on Thursday. There was no immediate response from the RSF to the proposal from the Intergovernmental Authority on Development (IGAD), a regional bloc.