TOKYO, Japan - President Joe Biden vowed Monday that US forces would defend Taiwan militarily if China attempted to take control of the island by force, prompting Beijing to warn that America was "playing with fire."

Speaking in Tokyo, Biden compared China's threat to self-ruled Taiwan to the Russian invasion of Ukraine, delivering his strongest remarks to date on the issue amid rising tensions over Beijing's growing economic and military power.

Asked if Washington was willing to get involved militarily to defend Taiwan, he gave the unequivocal reply: "Yes... That's the commitment we made."

"We agreed with the One China policy, we signed on to it," Biden said -- referring to Washington's diplomatic recognition of Beijing as the sole government of China.

"But the idea that it can be taken by force is just not appropriate," he said of Taiwan. "It would dislocate the entire region and would be another action similar to Ukraine."

Beijing, which considers Taiwan a rebellious province and has recently intensified military pressure on the island, warned that Washington is playing a risky game.

Foreign ministry spokesman Wang Wenbin declared that China "has no room for compromise or concession," when it comes to its sovereignty and territorial integrity.

The United States is "playing with fire," warned the Chinese State Council's Taiwan Affairs Office.

Washington is "using the 'Taiwan card' to contain China, and will itself get burned," said Zhu Fenglian, a spokeswoman for the office.

Zhu "urged the United States to stop any remarks or actions" that violate previously established principles between the two countries.

- Comparing Taiwan to Ukraine -
Biden's remarks, in a press conference together with Japanese Prime Minister Fumio Kishida, offered democratic Taiwan its loudest reassurance in decades but also brought more uncertainty to the US stance.

Since switching recognition to Beijing in 1979, the United States has committed to providing Taiwan with the means to defend itself but has kept a "strategic ambiguity" on whether it would intervene militarily.

The policy was designed both to keep Beijing from declaring war and to stop Taiwan from formally declaring independence.

But a growing constituency in the United States advocates a switch to "strategic clarity," believing an explicit promise to defend Taiwan is needed to deter an increasingly assertive and powerful Beijing.

Biden compared Taiwan's situation directly with Ukraine, which has received billions of dollars worth of arms and aid from the United States since the Russian invasion on February 24.

He said Western sanctions on Russia must exact a "long-term price," because otherwise "what signal does that send to China about the cost of attempting to take Taiwan by force?"

He warned Beijing was already "flirting with danger right now by flying so close and all the manoeuvres undertaken" -- referring to a growing number of Chinese sorties, naval exercises and other power projections in the Taiwan Straits.

- 'Policy has not changed' -
US Secretary of Defense Lloyd Austin insisted however that US "policy has not changed."

Biden "reiterated that policy, and our commitment to peace and stability across the Taiwan Strait," Austin said.

"He also highlighted our commitment under the Taiwan Relations Act, to help provide Taiwan the means to defend itself," he added.

Biden's remarks overshadowed his rollout of a new, 13-nation regional trade framework aimed at offsetting Chinese commercial power as well as Tuesday's meeting of the Quad group, an endeavor by India, Australia, Japan and the US to check China's growing naval power in the Indo-Pacific region.

Kishida meanwhile called for stability in the Taiwan Strait and said Tokyo was committed to boosting its defence spending.

"Japan will fundamentally strengthen its defence capacity, and to back that up will significantly increase its defence spending," he said.

"We don't rule out any options, including (acquiring) the capacity to counter-attack," he added.