Sudan's warring generals have agreed to send representatives for negotiations, potentially in Saudi Arabia, the United Nations' top official in the country told The Associated Press on Monday, even as the two sides clashed in the capital despite another three-day extension of a fragile ceasefire. The talks would initially focus on establishing a “stable and reliable” ceasefire monitored by “national and international” observers, Volker Perthes said. A string of temporary truces over the past week has de-escalated fighting only in some areas, while in others, fierce battles have continued to drive civilians from their homes and push the country into a humanitarian crisis. Perthes cautioned that logistics for talks were still being worked out. So far, only the military has announced it is prepared to join negotiations, with no public word from its opponent, the paramilitary Rapid Support Forces. Any talks would be the first major sign of progress since fighting erupted on April 15 between the army, led by Gen. Abdel Fattah Burhan, and the RSF, led by Gen. Mohammed Hamdan Daglo. Around 530 people, including civilians and combatants, have been killed since, with another 4,500 wounded, the Sudanese Health Ministry said. The United States, meanwhile, conducted its first evacuation of American civilians from Sudan. Watched over by US military drones, a group of Americans made the perilous journey by road from the capital, Khartoum, to the Red Sea city of Port Sudan. On Monday, a US Navy fast transport ship took 308 evacuees from Port Sudan to the Saudi port of Jeddah, according to Saudi officials. Explosions and gunfire echoed in parts of Khartoum and its neighboring city, Omdurman, on Monday, residents said. The two sides announced late Sunday they would abide by a 72-hour extension of their nominal ceasefire of the past week. The United States and Saudi Arabia have led a concerted international campaign to get the general to stop fighting, then engage in deeper negotiations to resolve the crisis. Speaking from Port Sudan, the UN envoy Perthes said they are still face daunting challenges in getting the two sides to abide by the truce. “It’s still important to connect both sides and have both sides commit to a ceasefire so that it is clear that fighting and taking action and moving forward and trying to gain ground is actually a violation of the ceasefire,” he said. One possibility was to establish a mechanism to monitor a ceasefire that includes Sudanese and foreign observers, “but that has to be negotiated,” he said. Talks on entrenching the ceasefire could take place in either Saudi Arabia or South Sudan, he said, adding that the former may be easier logistically since it has close ties to both sides. But even talks in Saudi Arabia has challenges, he said, since each side needs safe passage through territory of the other to reach talks. "That is very difficult in a situation where there is a lack of trust,” he said. The battle between the generals for control has plunged Sudan into chaos. Tens of thousands of Sudanese fled the fighting, especially in Khartoum and Omdurman. Many headed to the norther borders with Egypt or to Port Sudan. Foreign governments also evacuated their citizens from Sudan. Many fear the fighting could spiral further, dragging in others in a country where multiple armed groups exist and have fought several civil wars over the past decade. “There is a risk, that if this continues, that in the shadow of this war between two militaries, other forces, tribal forces, political forces are being mobilized and would take sides in an opportunistic way,” Perthes said.