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STORY: "This was not a gaffe," David Sacks of the Council on Foreign Relations, told Reuters.

"If China were to uses force against Taiwan, there is really only one person who would decide whether the United States comes to Taiwan's defense, and that is the president of the United States. It is not a spokesperson at the White House or the State Department. It is not a National Security Council official. It's the president," Sacks said.

While Washington is required by law to provide Taiwan with the means to defend itself, it has long followed a policy of "strategic ambiguity" on whether it would intervene militarily to protect Taiwan in the event of a Chinese attack.

A reporter asked Biden at a joint news conference with Japanese Prime Minister Fumio Kishida in Tokyo on Monday if the United States would defend Taiwan if it were attacked. "Yes," the president answered.

"That's the commitment we made," said Biden, who helped build an international coalition trying to thwart Russia's invasion of Ukraine.

"We agree with a one-China policy. We've signed on to it and all the intended agreements made from there. But the idea that, that it (Taiwan) can be taken by force, just taken by force, is just not, is just not appropriate," he said.

Biden added it was his expectation that such an event would not happen or be attempted.

But the comment was likely to be closely watched in a region worried about China's rising influence. China has been a key topic for Biden on his inaugural trip to Asia.