WASHINGTON — The U.S. Trade Representative (U.S.T.R.) on Sept. 17 unveiled a list of approximately $200 billion worth of Chinese imports that will be subject to additional tariffs. In accordance with the direction of President Donald Trump, the additional tariffs will take effect Sept. 24 and initially will be in the amount of 10%. The level of the additional tariffs will increase to 25% on Jan. 1, 2019, the U.S.T.R. said.

The list contains 5,745 full or partial lines of the original 6,031 tariff lines that were on a proposed list of Chinese imports announced on July 10. The U.S.T.R. said changes to the proposed list were made after U.S.T.R. and the interagency Section 301 Committee sought and received comments over a six-week period and testimony during a six-day public hearing in August.

“We are taking this action today as a result of the Section 301 process that the U.S.T.R. has been leading for more than 12 months,” Mr. Trump said. “After a thorough study, the U.S.T.R. concluded that China is engaged in numerous unfair policies and practices relating to United States technology and intellectual property — such as forcing United States companies to transfer technology to Chinese counterparts. These practices plainly constitute a grave threat to the long-term health and prosperity of the United States economy.”

Mr. Trump said if China takes any retaliatory actions against U.S. farmers or other industries, the United States will look to impose tariffs on approximately $267 billion of additional imports.

“As president, it is my duty to protect the interests of working men and women, farmers, ranchers, businesses and our country itself,” he said. “My administration will not remain idle when those interests are under attack.

“China has had many opportunities to fully address our concerns.  Once again, I urge China’s leaders to take swift action to end their country’s unfair trade practices. Hopefully, this trade situation will be resolved, in the end, by myself and President Xi of China, for whom I have great respect and affection.”

In response to the tariffs, the Chinese Ministry of Commerce on Sept. 18 said it would levy tariffs of between 5% and 10% on $60 billion in U.S. goods.