US President Joe Biden has said the US would intervene militarily if China was to invade Taiwan, saying the burden to protect Taiwan is "even stronger" after Russia's invasion of Ukraine.
President Biden said "yes" at a news conference in Tokyo when asked if he was willing to get involved militarily to defend Taiwan if China invaded.
"That's the commitment we made," he added.
Taiwan Relations Act
Traditionally, the US has avoided making such an explicit security guarantee to Taiwan, a country with which it no longer has a mutual defence treaty.
This was one of the most forceful presidential statements supporting self-governing in decades.
The 1979 Taiwan Relations Act, which has governed US relations with the island, does not require the US to step in militarily to defend Taiwan if China invades.
However, it makes it American policy to ensure Taiwan has the resources to defend itself and prevent any unilateral change of status in Taiwan by Beijing.
Mr Biden's comments were likely to draw a sharp response from the mainland, which has claimed Taiwan to be a rogue province.
A White House official said Mr Biden's comments did not reflect a policy shift.
Threat of China
Speaking alongside Japanese Prime Minister Fumio Kishida, Mr Biden said any effort by China to use force against Taiwan would "just not be appropriate"
He added that it "will dislocate the entire region and be another action similar to what happened in Ukraine".
China has stepped up its military provocations against democratic Taiwan in recent years aimed at intimidating it into accepting Beijing's demands to unify with the communist mainland.
"They're already flirting with danger right now by flying so close and all the manoeuvres that are undertaken," Mr Biden said of China.
Mr Biden said it is his "expectation" that China would not try to seize Taiwan by force.
He said that assessment "depends upon just how strong the world makes clear that that kind of action is going to result in long-term disapprobation by the rest of the community".
He added that deterring China from attacking Taiwan was one reason why it is important that Russian President Vladimir Putin "pay a dear price for his barbarism in Ukraine", lest China and other nations get the idea that such action is acceptable.
Mr Biden's comments came just before he formally launched a long-anticipated Indo-Pacific trade pact that excludes Taiwan.
White House national security adviser Jake Sullivan confirmed that Taiwan is not among the governments signed up for the Indo-Pacific Economic Framework.
The framework is meant to allow the US to work more closely with key Asian economies on issues such as supply chains, digital trade, clean energy and anti-corruption.
China would have been irritated at the inclusion of Taiwan.
Mr Sullivan said, however, that the US wants to deepen its economic partnership with Taiwan on a one-to-one basis.