BEIJING (AP) — Beijing imposed sanctions on Friday against 20 U.S. defense-related companies and 10 executives, a week after Washington annoucned large-scale arms sales to Taiwan.

The sanctions entail freezing the companies’ assets in China and banning individuals and organizations from dealing with them, according to the Chinese foreign ministry.

The companies include Northrop Grumman Systems Corporation, L3Harris Maritime Services and Boeing in St. Louis, while defense firm Anduril Industries founder Palmer Luckey is one of the executives sanctioned, who can no longer do business in China and are barred from entering the country. Their assets in the East Asian country have also been frozen.

The announcement of the U.S. arms-sale package, valued at more than $10 billion, has drawn an angry response from China, which claims Taiwan as its own and says it must come under its control.

If approved by the American Congress, it would be the largest-ever U.S. weapons package to the self-ruled territory.

“We stress once again that the Taiwan question is at the very core of China’s core interests and the first red line that must not be crossed in China－U.S. relations,” the Chinese foreign ministry said in a statement on Friday. “Any company or individual who engages in arms sales to Taiwan will pay the price for the wrongdoing.”

The ministry also urged the U.S. to stop what it called “the dangerous moves of arming Taiwan.”

Taiwan is a major flashpoint in U.S.-China relations that analysts worry could explode into military conflict between the two powers. China says that the U.S. arms sales to Taiwan would violate diplomatic agreements between China and the U.S.

China’s military has increased its presence in Taiwan’s skies and waters in the past few years, holding joint drills with its warships and fighter jets on a near-daily basis near the island.

Under the American federal law, the U.S. is obligated to assist Taiwan with its self-defense, a point that has become increasingly contentious with China. Beijing already has strained ties with Washington over trade, technology and other human rights issues.