France's largest sugar maker Tereos had to slow output slightly at some factories after TotalEnergies said ongoing strikes at its refineries would prevent it from supplying diesel fuel until the end of the week, a spokesperson said on Thursday. Strikes over wage demands have disrupted the French oil giant's products refining and delivery for the third day on Thursday, threatening supplies at a time of deepening energy instability. "TotalEnergies has warned us yesterday that we would not be supplied this week," a Tereos spokesperson said in answer to a Reuters question. This comes just as French sugar producers are trying to speed up production ahead of possible energy restrictions or shortages this winter if Russia cuts off gas supplies. Sugar production is among the most energy-intensive industries. French factories, which usually run between mid-September to late January or early February, are highly reliant on gas to transform their sugar beets into the sweetener.