The US expressed concern about China putting pressure on Taiwan, announcing to strengthen relations between Washington and Taipei.

"The United States is concerned about China's efforts to intimidate Taiwan. We urge Beijing to stop applying military, diplomatic and economic pressure on Taipei, and instead engage with it."

Washington vowed to support allies to promote security and prosperity in the Indo-Pacific, including strengthening relations with Taipei.

The announcement came after the Taiwan defense agency said eight H-6K bombers, four J-16 fighters and one Chinese Y-8 submarine hunting plane entered the southwest corner of the receiving zone.

China has always viewed Taiwan as part of a territory awaiting reunification.

The move by China comes days after the inauguration of US President Joe Biden.

After the event, White House National Security Council spokesman Emily Horne said the US's commitment to Taiwan was "sustainable".

Under the administration of former President Donald Trump, the relationship between the US and Taiwan is increasingly warm, while US-China or China-Taiwan relations are always tense.