WASHINGTON, United States -- President Joe Biden said Sunday that US forces would defend Taiwan against a Chinese invasion, while the White House said Washington's policy was unchanged.

Asked by the CBS "60 Minutes" program whether US troops would defend Taiwan, Biden said "yes," if it were "an unprecedented attack."

This was not the first time that Biden has declared US forces would take part in a war between China and Taiwan, with the White House appearing to walk back his comments afterward. The previous time was in May during a visit to Japan.

That time, Biden was also asked whether he'd commit US troops to such a situation and again he said "yes."

"That's the commitment we made," he said.

Washington cut formal diplomatic relations with Taiwan in 1979, switching recognition to Beijing as the sole representative of China. But at the same time, the United States maintained a decisive, if delicate role in supporting Taiwan.

Under a law passed by Congress, the United States is required to sell Taiwan military supplies to ensure its self-defense against Beijing's vastly larger armed forces.

But Washington has maintained what is officially called "strategic ambiguity" on whether it would intervene militarily.

The policy is designed both to ward off a Chinese invasion and discourage Taiwan from ever provoking Beijing by formally declaring independence.

Asked if the latest statement from Biden signaled a change in that strategic ambiguity, a White House spokesman said: "The president has said this before, including in Tokyo earlier this year. He also made clear then that our Taiwan policy hasn’t changed. That remains true."

Following his Tokyo assertion that "yes," US forces would be involved, Biden was subsequently asked if the strategic ambiguity concept was dead and he replied: "no."

Each time Biden has raised the possibility of US troops fighting to protect Taiwan, China has reacted furiously.

Tensions are already higher than usual in the wake of a rare visit to Taiwan by Nancy Pelosi, a key Biden ally and speaker of the US House of Representatives.

Although US politicians regularly go to Taiwan to show solidarity with the democratically elected government there, Pelosi's position puts her second in line to the US presidency.

China saw her visit as an escalation and reacted by mounting intimidating sea and air military exercises around Taiwan.

In a recent move by the other chamber of Congress, a US Senate committee last Wednesday took the first step toward changing current policy by seeking to directly allocate $4.5 billion in military assistance over four years for Taiwan, instead of simply continuing to sell arms to the island.