(Reuters) - The FTSE 100 blue-chip stock index dropped more than 1% on Thursday, under pressure from results-driven falls in Shell and Lloyds and the latest tensions over the U.S.-China trade situation. The main index ended 1.1% lower on its worst day in a month, lagging its European counterparts, while losses in the domestically focused FTSE 250 were capped at 0.5% in response to stronger sterling.A report that Chinese officials have doubts over sealing a comprehensive long-term trade deal..