Fighting on both sides of the Chad-Sudan border has sparked a new influx of refugees and threatens aid to thousands who had fled violence in Sudan's western Darfur region, the UN food aid agency warned yesterday. Most of the people affected by recent clashes between government troops and rebels only have enough food to last them a month or two, the World Food Program said, appealing for urgent financial support to stem an even bigger humanitarian crisis.The warning came days after Chadian troops launched a major offensive against rebels who had set up bases along the unstable frontier. The operation came on top of raids into eastern Chad by armed groups involved in a civil war that has devastated Darfur. "We are at an extremely delicate stage in Chad — right on the edge," Stefano Porretti, WFP's Country Director, said.