"The Chinese side expresses its utmost discontent and strong protest over the US plans to sell arms to the Taiwanese side, and has already lodged a related representation to the US side," Geng said at a press briefing.
He called the US to move a serious breach of the international law and international relations standards, which also threatened China's sovereignty and security.
"The Chinese side is strongly urging [the United States] to abandon the plan on arms deliveries to Taiwan and to cease the US-Taiwan military ties in order to avoid significant damage to the Chinese-US trade relations, peace and stability in the Taiwan Strait, as well as the Chinese-US cooperation in different areas," Geng said.
China has been repeatedly calling on other countries to cut their ties with Taiwan. It has already slammed the United States for maintaining informal diplomatic relations with Taiwan and selling weapons to the region in spite of formally sticking to the "One China" policy stipulating that Taiwan is a Chinese territory.
In March, US President Donald Trump signed the Taiwan Travel Act that sought to stimulate visits between officials from Taiwan and the United States. The Chinese Defense Ministry then said it was viewing the move as direct interference in China's domestic affairs.
The situation is exacerbated by the fact that China and the United States have been engaged in a trade war for several months.