BEIJING/LOS ANGELES — The U.S. and China on Tuesday began charging additional port fees on ocean shipping firms that move everything from holiday toys to crude oil, making the high seas a key front in the trade war between the world’s two largest economies.

A return to an all-out trade war appeared imminent last week, after China announced a major expansion of its rare earths export controls and President Donald Trump threatened to raise tariffs on Chinese goods to triple digits.

But after the weekend, both sides sought to reassure traders and investors, highlighting cooperation between their negotiating teams and the possibility they could find a way forward.

China said it had started to collect the special charges on U.S.-owned, operated, built or flagged vessels but clarified that Ch

See Full Page