The US State Department approved the possible sales to Taiwan of M1A2T Abrams tanks, Stinger missiles and related equipment on Monday, Reuters reported.
Foreign Ministry spokesman Geng Shuang made the comments at a daily news briefing in Beijing.
Beijing views Taiwan as part of its territory and has previously expressed "serious concerns" about the possible sale, AFP reported.
Congress has been notified about the potential deal, which would include 108 M1A2T Abrams tanks, some 250 Stinger missiles, related equipment and support, according to the Defense Security Cooperation Agency (DSCA).
US lawmakers have 30 days to object to the sale but are unlikely to do so.
The proposed tank sale "will contribute to the modernization of the recipient's main battle tank fleet, enhancing its ability to meet current and future regional threats and to strengthen its homeland defense," DSCA said in a statement.
And the missiles would "support the foreign policy and national security of the United States by helping to improve the security and defensive capability of the recipient, an important force for political stability, military balance, and economic progress in the region," it said.
Neither would alter the "basic military balance in the region," according to DSCA.
Beijing registered its opposition to the possible sale earlier this month.
"We have repeatedly emphasized to the US to fully understand the extremely sensitive and damaging nature of their decision to sell arms to Taiwan, and abide by the One China principle," the Foreign Ministry spokesman said.