WASHINGTON • The United States is closely watching Chinese intentions towards Taiwan, concerned that Beijing's growing military prowess may increase the risk that it could one day consider bringing the self-ruled island under its control by force, a US official said.

The senior US defence intelligence official, who spoke on condition of anonymity, did not predict that China's military, known as the People's Liberation Army (PLA), would take such a step, but said such a possibility was the top worry as China expands and modernises its military capabilities.

"The biggest concern is that... they are getting to a point where the PLA leadership may actually tell (President) Xi Jinping that they are confident in their capabilities," the official said on Tuesday.

The official, asked if the reference was to Chinese confidence in their capabilities to be able to successfully win a battle with Taiwan, said: "Well, specifically, that would be the most concerning to me."

Taiwan is only one of a growing number of flashpoints in the US-China relationship, including a trade war, US sanctions on the Chinese military and China's increasingly muscular military posture in the South China Sea.

However, in meetings with Pentagon leaders, PLA officials have long described Taiwan as China's most sensitive issue.

China has repeatedly sent military aircraft and ships to circle the island on drills in the past few years and worked to isolate the island internationally, whittling down its few remaining diplomatic allies.

It has also strongly objected to the passage of US warships through the Taiwan Strait this year, and issued a terse warning about Taiwan after talks in Beijing on Tuesday with the US Navy's top officer, Admiral John Richardson.

In the talks, General Li Zuo-cheng, who is chief of China's Central Military Commission Joint Staff Department, stressed that Taiwan was "China's internal affairs", and that Beijing would allow "no external interference".

Washington has no formal ties with Taipei but is bound by law to help the island defend itself, and is Taiwan's main source of arms. The Pentagon says Washington has sold Taiwan more than US$15 billion (S$20 billion) in arms since 2010.

Mr Xi has stepped up pressure on the democratic island since Ms Tsai Ing-wen from the pro-independence Democratic Progressive Party became president in 2016.

On Jan 2, Mr Xi said in a speech that China reserved the right to use force to bring Taiwan under its control, but would strive to achieve peaceful reunification.

Still, the US defence intelligence official cautioned against over-reacting, noting that Mr Xi could believe he has plenty of time to achieve reunification with Taiwan.

REUTERS