China and the U.S. have quietly started negotiating to improve U.S. access to Chinese markets, after a week filled with harsh words from both sides over Washington’s threat to use tariffs to address trade imbalances, people with knowledge of the matter said.

The talks, which cover wide areas including financial services and manufacturing, are being led by Liu He, China’s economic czar in Beijing, and U.S. Treasury Secretary Steven Mnuchin and U.S. trade representative Robert Lighthizer in Washington.