The new arms package, which includes two navy frigates, antitank missiles, combat systems for minesweepers, amphibious attack vehicles and communications systems, is the first arms deal since 2011, and the third offered by President Obama, for a total of $14 billion. It does not include new F-16 jet fighters or submarines, two advanced offensive systems that would have undoubtedly riled Beijing even more.

China has so improved its military capabilities that Taiwan would not be able to repel a punishing airstrike or an invasion if Beijing decided to take that course. It has long been assumed that American weaponry, and the threat of a direct confrontation with the United States, would make China think twice about reckless military action.

China has threatened not to do business with American companies involved in the arms sales, but since American defense firms are barred from making military sales to China it is unclear how serious the effects would be.

The deal was negotiated with President Ma Ying-jeou of Taiwan’s ruling Nationalist Party, or Kuomintang, who has sought to improve ties with Beijing and met last month in Singapore with President Xi Jinping of China, the first time the leaders of Taiwan and China have met since before the Chinese Revolution. And its announcement comes a month before Taiwan’s presidential and parliamentary elections, which are expected to be won by the Kuomintang’s rival, the Democratic Progressive Party. The D.P.P. favors a more distant relationship with Beijing and the assertion of Taiwan’s own identity. Its secretary general, Joseph Wu, welcomed the arms deal and said stronger defense capabilities would give Taiwan more confidence to expand exchanges with China.