A senior Chinese army officer warned Thursday that Beijing “will not sit idly by” if the U.S. proceeds with a planned sale of F-16 fighter jets to Taiwan, saying the country could consider action beyond sanctioning firms associated with the deal.

“China will not sit idly by,” Col. Chen Rongdi, chief of the Institute of War Studies at the Academy of Military Sciences, said at a forum sponsored by China’s official journalists’ association, according to The Associated Press. “Of course, we don’t rule out additional measures.”

Chen did not clarify what additional measures China might take, the news service noted.

ADVERTISEMENT

Col. Cao Yanzong, a research fellow at the institute, added that the sale would “further [undermine] relations between China and the U.S. and China and Taiwan.”

The warning comes a day after China threatened to sanction any U.S. firm affiliated with the $8 billion sale to Taiwan, an autonomous island that Beijing considers to be under its rule.

The Trump administration on Tuesday formally notified Congress of the sale of 66 fighters to Taiwan. The deal is not expected to be impeded on Capitol Hill, where Taiwan enjoys bipartisan support, and the State Department approved the sale this week.

Secretary of State Mike Pompeo Michael (Mike) Richard PompeoWatchdog confirms State Dept. canceled award for journalist who criticized Trump Trump's push for win with Sudan amps up pressure on Congress Putin nominated for Nobel Peace Prize MORE on Monday seemed to downplay the sale, the first to Taiwan since the George H.W. Bush administration, saying it is “deeply consistent with the arrangements, the historical relationship between the United States and China.”

“Our actions are consistent with past U.S. policy. We are simply following through on the commitments we’ve made to all of the parties,” he said during a Fox News interview.

The planned sale comes as Beijing ramps up pressure on Taiwan, saying it is prepared for war if the island declares independence, running encirclement drills around the territory and flying jets across their maritime border, according to Reuters.

Taiwanese President Tsai Ing-wen’s Cabinet last week approved an 8.3 percent increase in military spending for the year starting in January.