President Donald Trump in a series of tweets on Friday, Aug. 23, ordered all U.S. companies with operations in China to begin looking for alternatives in response to retaliatory tariffs from Beijing.

The president started by tweeting, “Our Country has lost, stupidly, Trillions of Dollars with China over many years. They have stolen our Intellectual Property at a rate of Hundreds of Billions of Dollars a year, & they want to continue. I won’t let that happen! We don’t need China and, frankly, would be far better off without them.”

He continued, “The vast amounts of money made and stolen by China from the United States, year after year, for decades, will and must STOP. Our great American companies are hereby ordered to immediately start looking for an alternative to China, including bringing your companies HOME and making your products in the USA.”

The president also called for UPS, Federal Express, and Amazon to block any deliveries from China of the powerful opioid drug fentanyl.

Trump said that he will respond in hours to an announcement Friday that China was retaliating to U.S. tariffs with a slate of its own protective measures.

“I will be responding to China’s Tariffs this afternoon. This is a GREAT opportunity for the United States. Also, I am ordering all carriers, including Fed Ex, Amazon, UPS and the Post Office, to SEARCH FOR & REFUSE, all deliveries of Fentanyl from China (or anywhere else!). Fentanyl kills 100,000 Americans a year. President Xi said this would stop—it didn’t. Our Economy, because of our gains in the last 2 1/2 years, is MUCH larger than that of China. We will keep it that way!” Trump added.

Early on Friday, China said it would put into place tariffs on $75 billion in U.S. products in retaliation for the Trump administration’s latest planned tariff hikes.

Tariffs of 10% and 5% will take effect on two batches of goods on Sept. 1 and Dec. 15. Beijing mentioned cars and auto parts but gave no further details of what goods would be affected but the timing matches Trump’s planned hikes.

Earlier, President Trump announced plans to raise tariffs Sept. 1 on $300 billion of Chinese products after talks broke down in May. Increases on some goods were postponed to Dec. 15.

The Dow Jones Industrial Average sank more than 300 points after the president made the announcements on Twitter.

Includes reporting from the Associated Press.