The United States approved a $ 330 million sale of fighter jets and other aircraft parts to Taiwan on Thursday, and this became the first deal of this kind since President Donald Trump took office in January, eliciting gratitude from Taipei and strong criticism from Beijing.

The Pentagon, in a statement, said, "the proposed sale will improve the recipient's capability to meet current and future threats by maintaining the operational readiness of the recipient's fleet of F-16, C-130," and other aircraft.

Washington maintains official diplomatic relations with Beijing, but it also keeps unofficial ties with Taiwan and continues to be the island's main arms supplier, and United States law requires the country to provide Taiwan with the tools it needs for its defence.

Taiwan's presidential office said this was the first arms deal announced by the current administration and thanked the United States government for upholding its policy of regular arms sales to Taiwan and for supporting the island as it tries to strengthen its self-defence capacity and resilience.

Presidential office spokesperson Karen Kuo said, "The deepening of the Taiwan-U.S. security partnership is an important cornerstone of peace and stability in the Indo-Pacific region."

Taiwan's defence ministry said in a statement that the sales were expected to "take effect" within one month.

The ministry said that these parts will help the air force maintain its fighter readiness, support air defences, improve defensive resilience and strengthen the island's ability to respond to China's "grey-zone" incursions.

China's military carries out regular missions in the waters and skies around Taiwan, which the government in Taipei describes as "grey-zone" activities meant to exert pressure but still stopping short of direct conflict.

China reacted with anger, as it usually does whenever the United States sells arms to Taiwan.

Foreign ministry spokesperson Lin Jian told reporters in Beijing, "The Taiwan question is the core of China's core interests and the first red line that must not be crossed in China-U.S. relations."

China considers Taiwan, which is democratically governed, as part of its territory and has not ruled out using force to gain control, while Taiwan's government rejects China's sovereignty claims and says that only the people of Taiwan can decide their own future.

Trump says Chinese President Xi Jinping has told him that he will not invade Taiwan while the Republican leader is in office.

The announcement of the possible arms sale came after Trump and Xi met late last month in South Korea for a trade agreement. Ahead of the meeting, many in Taipei feared a risk of a "selling out" of Taiwan's interests by Trump to Xi.