The two biggest economies in the world have been putting more taxes on each other's products. This started after the U.S. put higher taxes on goods from many countries. China has to pay 145% taxes on things they send to the U.S. But most other countries did not have to pay these taxes for 90 days.

On Wednesday, China said its economy grew by 5.4% in the first three months of the year, helped by strong exports. But experts think China's economy will slow down a lot in the next few months because of new taxes on goods coming from China to the U.S.

Exports helped China's economy grow by 5% last year. This year, China wants it to grow by about 5% again.

Beijing put a big tax on some things from the U.S. Beijing also said it wants its markets to be open for trade and for people to invest money.

Sheng Laiyun said the taxes will make China's economy a little weaker now, but they will not stop it from growing later.

It was not clear why China changed who was doing the talking. This change happened when China said it had many ways to answer the U.S. China can use its own big market with 1.4 billion people. It can also work with Europe and countries in the south of the world. But people in China are not buying much, so it will be hard to find another buyer like the U.S.

China also put more limits on sending out rare earths. Rare earths are special materials used in high-tech things, making airplanes, and for the military.

Before his new job, Li was China's ambassador to the World Trade Organization for about four and a half years. This organization controls trade around the world. Beijing used it to complain about the taxes on goods from the U.S.

He also worked for China at the United Nations in Geneva and other international groups in Switzerland.

He also worked as an assistant minister in the Ministry of Commerce and was in charge of their department for rules and agreements.

Li studied law at a good university in China called Peking University. He also studied economics of law at the University of Hamburg.