Chinese state media are warning of “severe consequences” if the United States goes ahead with a reported plan to upgrade Taiwan's existing fleet of F-16 fighter jets.

U.S. lawmakers say they have been briefed on the plan, which falls short of Taiwan's request to purchase the latest generation F-16s with more advanced capabilities and weapons.

The China Daily newspaper said Monday that even the reduced $4.2 billion arms package will provoke a fierce reaction from China, affecting its relations with Taiwan and the United States. It quoted a financial news website suggesting that China reduce its huge holdings in U.S. Treasury bonds.

A Chinese foreign ministry spokesman said in Beijing that China's opposition to U.S. arms sales to Taiwan has been “consistent and clear.”

Obama administration officials say they will not comment on the sale until they have formally notified Congress — something that is expected before the end of this month.

China considers Taiwan a renegade province, and has threatened to use force against the island if it ever formally declares independence.

The United States has no official diplomatic ties with Taiwan, but U.S. law obliges Washington to sell the island defensive weapons.