China has threatened to impose sanctions on U.S. companies involved in arms sales with Taiwan after the Trump administration said it supported an $8 billion deal to the island.

The Defense Security Cooperation Agency said in a statement Tuesday, Aug. 20, that the State Department had made a determination approving a possible sale of 66 F-16C/D Block 70 aircraft and related equipment and support as requested by Taiwan.

The agency said the proposed sale would serve U.S. interests by supporting Taiwan’s efforts to modernize its armed forces, improve its security, and help maintain political stability, military balance, and economic progress in the region. It would also help Taiwan enhance its airspace defense and interoperability with the United States.

The defense agency also stressed that the proposed arms sale would not alter the basic military balance in the region.

This sale of fighter jets is the fourth package of arms sales to Taiwan from the Trump administration, according to NPR.org.

China has raised its voice to oppose the U.S. arms deal to Taiwan, which Beijing considers a part of its territory and should be reunited with the mainland.

NPR quoted a Chinese state media report that said China’s Foreign Ministry, on Wednesday, Aug. 21, warned that China would impose sanctions if the arms sales go forward.

Though Beijing often claims Taiwan is an inseparable part of China’s territory, the island has had de facto independence from China since the end of a civil war in 1949.

When the United States switched its official diplomatic ties from Taipei to Beijing in 1979, it vowed to defend Taiwan if China attempted to take the island by force.

A series of pro-democracy protests in Hong Kong over the past few months has also been sounding alarms for Taiwan to enhance its opposition to China’s “one country, two systems.”