The United States has approved the potential sale of $619 million in new weapons to Taiwan, including missiles for its F-16 fleet, as the island reported a second day of large-scale Chinese air force incursions nearby.

The arms sales are likely to further sour already tense ties between Washington and Beijing, which has repeatedly demanded such deals stop, viewing them as unwarranted support for democratically governed Taiwan, an island China claims as its own territory.

The Pentagon said on Wednesday the US State Department has approved the potential sale to Taiwan of arms and equipment that includes 200 anti-aircraft Advanced Medium Range Air-to-Air Missiles (AMRAAM) and 100 AGM-88B HARM missiles that can take out land-based radar stations.

“The proposed sale will contribute to the recipient’s capability to provide for the defence of its airspace, regional security, and interoperability with the United States,” it said in a statement.

Taiwan’s defence ministry said the missiles would help “effectively defend the airspace to deal with threats and provocations from the Communist military” and would bolster defence stockpiles.

Raytheon Technologies (RTX.N) and Lockheed Martin (LMT.N) are the principal contractors, it added. China has sanctioned both companies for selling Taiwan weapons.

China’s Foreign Ministry said it was “firmly” opposed to the planned sale, adding that the United States should stop arms sales to and military contacts with Taiwan.

CHINESE AIR FORCE INCURSION

Taiwan has complained for the past three years or so of stepped-up Chinese military activities near the island as Beijing seeks to assert its sovereignty claims.

Taiwan reported on Thursday a second day of large-scale Chinese air force incursions into its air defence identification zone, with its defence ministry saying that during the last 24 hours, it had spotted 21 aircraft.

China has said its activities in the area are justified as it seeks to defend its territorial integrity and to warn the United States against “colluding” with Taiwan, despite the anger this causes in Taipei.

Taiwan’s defence ministry said the aircraft, 17 J-10 fighters and four J-16 fighters, had flown into the southwestern corner of Taiwan’s air defence identification zone, according to a map the ministry released.

The J-10s, an older model that entered service two decades ago, flew closer to the Chinese coast than Taiwan’s, while the J-16s, a much newer and more advanced fighter, flew northeast of the Taiwan-controlled Pratas Islands, the map showed.

The lightly defended Pratas is strategically located at the top of the South China Sea, and many of China's fly-bys happen nearby.

Taiwan’s forces monitored the situation, including sending up its own planes, the ministry added, using the normal phrasing for its response to such Chinese incursions.

The ministry on Wednesday reported 19 Chinese aircraft flying in Taiwan’s air defence zone.

None of the aircraft crossed the sensitive median line of the Taiwan Strait, which has served as an unofficial barrier between the two sides, but which China’s air force has been flying over almost daily since staging war games near Taiwan last August.

Taiwan last reported a large median line crossing of Chinese aircraft on Friday, when 10 planes were involved.

China has not commented on recent activities near Taiwan. In January, China said it staged combat drills around the island to “resolutely counter the provocative actions of external forces and Taiwan independence separatist forces”.

No shots have been fired and the Chinese aircraft have been flying in Taiwan’s ADIZ, not in its territorial airspace.

The ADIZ is a broader area Taiwan monitors and patrols which gives it more time to respond to any threats.

Taiwan’s government has repeatedly offered talks with China but says the island will defend itself if attacked and that only the Taiwanese people can decide their own future.