President Joe Biden participates in a CNN town hall session in Baltimore on Thursday. AP

The United States will defend Taiwan if China attacks it, President Joe Biden said, prompting a warning from Beijing on Friday that its determination to take back the democratic island should not be underestimated.

Authoritarian China regards self-ruled Taiwan as its own territory and has vowed to one day seize the island, by force if needed.

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Earlier, the White House on Friday reiterated that Joe Biden was not signaling a change in US policy toward Taiwan.

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.

Meanwhile, North Korea on Saturday accused the Biden administration of raising military tensions with China through its "reckless” backing of Taiwan, and said that the growing US military presence in the region constitutes a potential threat to the North.

In comments carried by state media, North Korea Vice Foreign Minister Pak Myong Ho criticised the United States for sending warships through the Taiwan Strait and providing Taiwan with upgraded weapons systems and military training.

A Chinese PLA J-16 fighter jet flies to an undisclosed location. File/AP

The United States’ "indiscreet meddling” in issues regarding Taiwan, which the North sees as entirely a Chinese internal affair, threatens to touch off a "delicate situation on the Korean Peninsula.”

"The US government has demonstrated, through actual actions, their rock solid support for Taiwan," Presidential Office spokesperson Xavier Chang said in a statement.

But Beijing warned that Biden's comments risked "damaging Sino-US relations," warning Washington on Friday to "act and speak cautiously on the Taiwan issue."

Legend-class US Coast Guard National Security Cutter Munro transits the Taiwan Strait. File/AP

"China has no room for compromise on issues involving its core interests," foreign ministry spokesman Wang Wenbin said at a regular press briefing.

Warplane incursions

China has ramped up economic, diplomatic and military pressure on Taiwan since the 2016 election of President Tsai Ing-wen, who views Taiwan as already sovereign and not part of "one China."

Military pressure has escalated in the last year with China sending waves of fighter jets and nuclear-capable bombers into Taiwan's air defense zone.

According to an AFP tally, more than 800 flights have been made into the zone since September last year -- 170 just this month.

Defending Taiwan, one of Asia's most progressive democracies, has become a rare bipartisan issue in Washington's otherwise deeply polarised landscape.

Chinese President Xi Jinping attends a meeting. File photo

At Thursday's live town hall, Biden was also asked by an audience member whether the United States would be able to keep up with China's rapid military development.

Biden responded with "Yes."

"Don't worry about whether... they're going to be more powerful," he said. "China, Russia and the rest of the world knows we have the most powerful military in the history of the world."

But Biden expressed concern that rival countries may "engage in activities where they may make a serious mistake."

He referred to his longtime relationship with Chinese President Xi Jinping and repeated his position that he does not want "to start a new Cold War with China."

But he warned: "I just want to make China understand that we are not going to step back."

Biden's comments also come in the wake of a Financial Times report that China has tested a state-of-the-art hypersonic missile with nuclear capacity that flew around the planet before landing, albeit not on target.