Trump said in a subsequent Twitter post that he would respond to China's tariffs later on Friday.

President Donald Trump reacted furiously on Friday after Federal Reserve Chair Jerome Powell spoke about the trade war with China and economic risks to the United States, asking whether his appointee to the US central bank was a greater "enemy" than China's leader Xi Jinping.

"As usual, the Fed did NOTHING! It is incredible that they can 'speak' without knowing or asking what I am doing, which will be announced shortly," Trump wrote on Twitter. We have a very strong dollar and a very weak Fed. I will work 'brilliantly' with both, and the U.S. will do great.

"My only question is, who is our bigger enemy, Jay Powel or Chairman Xi?"

Trump indicated he was planning to take an action that would affect the dollar and the Fed, but it was unclear what that would be. The president said in a subsequent Twitter post that he would respond to China's tariffs later on Friday.

China said on Friday it would impose retaliatory tariffs against about $75 billion worth of US goods, putting as much as an extra 10% on top of existing rates in the dispute between the world's top two economies.