The United States has approved the sale to Taiwan of $619 million in munitions for F-16 fighter jets, the Pentagon announced Wednesday, in a move China said "seriously damages" relations between Washington and Beijing.
The sale will boost Taiwan's "capability to provide for the defence of its airspace, regional security, and interoperability with the United States," the Pentagon said in a statement.
The package will include anti-radar missiles, advanced air-to-air missiles, launchers and dummy missiles to be used for training, it said.
The U.S. and China have increasingly sparred over Taiwan since a high-level U.S. visit to the self-ruled island -- which China claims as its territory -- last year.
Diplomatic tensions were further raised last month after the downing of a balloon over U.S. airspace that Washington said was a Chinese surveillance craft.
The U.S. State Department said separately that Wednesday's sale was consistent with Washington's One China Policy, in which the U.S. recognises Beijing, and acknowledges the Chinese position that Taiwan is part of China.
The Pentagon said the deal would "not alter the basic military balance in the region."
On Thursday, China condemned the sale, with a foreign ministry spokesperson saying it "seriously damages China's sovereignty and security interests, and seriously damages Sino-U.S. relations and peace and stability across the Taiwan Strait."
"China will continue to take resolute and forceful measures to firmly defend its sovereignty and security interests," spokesperson Mao Ning told reporters.
At least 54 Chinese warplanes were detected in airspace around Taiwan on Tuesday and Wednesday, according to the island's defence ministry, with 40 of those crossing into Taipei's air defence identification zone.
Chinese incursions into airspace around Taiwan have become increasingly common, with 275 aircraft reported to have done so this year, according to an AFP tally.
Taiwan welcomed its first U.S. arms deal of the year, which is the ninth so far under U.S. President Joe Biden.
"In the face of China's continued military expansion and provocative behaviour, Taiwan will continue to actively improve its self-defence capabilities," foreign ministry spokesman Jeff Liu said.