China said Monday it would impose sanctions on Lockheed Martin, a Boeing defence division and other US firms involved in arms sales to Taiwan, the self-governed island that Beijing views as its territory.
The two US giants were involved in a recent sale of nearly $2 billion worth of missiles to Taiwan, alongside Raytheon, and foreign ministry spokesman Zhao Lijian urged the US to stop arms sales to the island.
The status of Taiwan holds potential for conflict between the United States and China, during a wider struggle for technology, security and trade supremacy.
Beijing says Taiwan is an inviolable part of China to be reclaimed, by force if necessary.
Zhao said the sanctions were "to safeguard national interests" and would apply to those who have "behaved badly in the process of arms sales to Taiwan".
"We will continue to take necessary measures to safeguard national sovereignty and security interests," said Zhao, without giving further details on the sanctions.
Under the administration of President Donald Trump the US has brought Taiwan into play as part of a wider diplomatic and economic squeeze of its rival, sending high-level envoys and boosting arms sales.
The State Department said last week it had approved the sale of 135 air-to-ground missiles, in a move welcomed by Taiwan.
Also approved was the sale of six MS-110 air reconnaissance pods and 11 M142 mobile light rocket launchers, taking the value of the three arms packages to $1.8 billion.
- 'Future threats' -
Beijing has ramped up diplomatic and military pressure on Taiwan since the 2016 election of President Tsai Ing-wen, who views the island as a de facto sovereign nation and not part of "One China".
A statement from the US State Department last week said the SLAM-ER missiles would help Taiwan "meet current and future threats".
The missiles provide "all-weather, day and night, precision attack capabilities against both moving and stationary targets" on the ground or ocean, the statement added.
Taiwan's defence ministry said the weapons would help it "build credible combat capabilities and strengthen the development of asymmetric warfare".
Chinese fighter jets and bombers have entered Taiwan's air defence zone with increasing frequency in recent months, while propaganda films have shown simulated attacks on Taiwan-like territories.
China has also launched a diplomatic offensive aimed at courting Taiwan's few official allies, persuading the Solomon Islands and Kiribati to switch sides last year.
Earlier this month a top White House official urged Taiwan to build its military capabilities to protect against a possible invasion by China.
Beijing in turn has accused Washington of violating agreements signed in the 1970s establishing diplomatic relations between the two governments.
China has sanctioned Lockheed for previous arms sales to Taiwan.