In April and May, Beijing squeezed global automakers with export curbs on a range of rare earths items and related magnets, while negotiators faced off over triple-digit US tariffs on goods from the world's second-largest economy. Four months on, after Washington and Beijing unexpectedly reprised threats of fresh tariffs and rare earth export curbs, worry is growing that China could return to the same playbook. That would mean it reneges on a June deal with the United States to ease the flow of critical minerals. China's shipments of rare earth magnets fell 6.1 percent in September from August, customs data showed on Monday, ending three months of gains, and dropping even before Beijing unveiled a dramatic expansion of its export...