Trump cannot legally compel U.S. companies to abandon China immediately and he gave no detail on how he might proceed with any such order, although he said he would be offering a response later on Friday to tariffs on American products announced by China earlier in the day.

The U.S. dollar rose sharply against the Chinese yuan, U.S. stock markets fell and oil prices dropped on Trump's latest salvo against China. "Our great American companies are hereby ordered to immediately start looking for an alternative to China, including bringing your companies HOME and making your products in the USA," Trump wrote on Twitter. "We don't need China and, frankly, would be far better off without them."