Since the US started putting higher taxes on goods from many countries, the two biggest economies in the world have been putting more and more taxes on each other's products. For example, China has to pay a 145% tax on goods it sells to the US, but most other countries were given a 90-day delay before the new taxes started.

On Wednesday, China announced that its economy grew by 5.4% in the first three months of the year, helped by strong exports. But experts think the economy will grow much slower in the next few months because of new taxes on goods coming from China to the US.

Exports greatly helped China achieve its 5% growth last year, and the government still plans for similar growth this year.

Beijing has responded to the U.S. by putting a 125% tax on American goods. At the same time, Beijing says it wants its markets to stay open for trade and investment.

Sheng Laiyun, a spokesperson for the National Bureau of Statistics, told reporters that the new taxes will cause problems for China's economy for a short time, but they will not stop its growth in the future.

It wasn't clear why China was changing the people doing the talks. This change happens as Chinese officials say they have different ways to respond to the US. For example, they could depend more on their large market of 1.4 billion buyers, and on Europe and countries in the southern part of the world. But because people in China are not buying much, it will be difficult to replace the American buyers.

China also put more limits on sending out rare earth materials. These materials are used in advanced electronics, making planes, and military equipment.

Before his new job, Li was China's representative at the World Trade Organization for about four and a half years. This organization manages trade around the world, and China has asked it for help with its disagreement about taxes on goods from the U.S.

He was also the second most important person in the Chinese team at the United Nations office in Geneva and other international groups in Switzerland.

He has also worked as an assistant minister at the Ministry of Trade and the head of the ministry's department for agreements and laws.

Li studied law at Peking University in China, which is a very famous university. He also has a master's degree in economics and law from the University of Hamburg.