TAIPEI/WASHINGTON (REUTERS) - Military tensions with China are at their worst in more than 40 years, Taiwan's defence minister said on Wednesday (Oct 6), days after record numbers of Chinese aircraft flew into the island's air defence zone.

Tensions have hit a new high between Taipei and Beijing, which claims the island as its own territory, and Chinese military aircraft have repeatedly flown through Taiwan's air defence identification zone.

Over a four-day period beginning last Friday, Taiwan reported close to 150 Chinese air force aircraft entered its air defence zone, part of a pattern of what Taipei calls Beijing's continued harassment of the island. Just one incursion was reported on Tuesday.

Asked by a lawmaker on the current military tensions with China at the parliament, Defence Minister Chiu Kuo-cheng said the situation was "the most serious" in more than 40 years since he joined the military, adding there was a risk of a "misfire" across the sensitive Taiwan Strait.

"For me as a military man, the urgency is right in front of me," he told a parliamentary committee reviewing a special military spending of T$240 billion (S$11.7 billion) for home-made weapons including missiles and warships.

China regards Taiwan as a renegade province awaiting reunification with the mainland, by force if necessary. Taiwan says it will defend its freedoms and democracy, blaming China for the tensions.

Chiu said China already has the ability to invade Taiwan and it will be capable of mounting a "full scale" invasion by 2025.

"By 2025, China will bring the cost and attrition to its lowest. It has the capacity now, but it will not start a war easily, having to take many other things into consideration."

Taiwan President Tsai Ing-wen also said on Wednesday at a meeting of her pro-independence Democratic Progressive Party: "Actions taken by... (China) have seriously damaged peace and stability in the region."

"I want to tell the authority in Beijing that it has to exercise restraint to avoid potential conflicts due to miscalculations or accidents," she added.

The United States, Taiwan's main military supplier, has confirmed its "rock-solid" commitment to Taiwan and also criticised China. Beijing blames Washington's policies of supporting Taiwan with arms sales and sending warships through the Taiwan Strait for raising tensions.

Taiwan's special military spending over the next five years will go mostly towards naval weapons including anti-ship weapons such as land-based missile systems.

Chiu's comments came after US President Joe Biden said on Tuesday that he has spoken to Chinese President Xi Jinping about Taiwan and they agreed to abide by the Taiwan agreement.

"I've spoken with Xi about Taiwan. We agree... we'll abide by the Taiwan agreement," he said. "We made it clear that I don't think he should be doing anything other than abiding by the agreement."

Biden appeared to be referring to Washington's long-standing "one China policy" under which it officially recognises Beijing rather than Taipei, and the Taiwan Relations Act, which makes clear that the US decision to establish diplomatic ties with Beijing instead of Taiwan rests upon the expectation that the future of Taiwan will be determined by peaceful means.

The comments to reporters at the White House were made after Biden's return from a trip to Michigan touting a spending package.

The United States urged China on Sunday to stop its military activities near Taiwan.

"The United States is very concerned by the People's Republic of China's provocative military activity near Taiwan, which is destabilising, risks miscalculations, and undermines regional peace and stability," State Department spokesperson Ned Price said in a statement on Sunday.

Biden also appeared to be referencing a 90-minute call he held with Xi on Sept 9, their first talks in seven months, in which they discussed the need to ensure that competition between the world's two largest economies does not veer into conflict.

In Paris on Wednesday, US Secretary of State Antony Blinken called China's recent actions around Taiwan "provocative and potentially destabilising", and urged leaders in Beijing to stop such behaviour for fear of a miscalculation.

"The actions we've seen by China are provocative and potentially destabilising," Blinken said in an interview in Paris with Bloomberg Television. "What I hope is that these actions will cease because there's always the possibility of miscalculation, of miscommunication, and that's dangerous."

"It's very important that no one take unilateral actions that change the status quo by force," Blinken said in the interview Wednesday, conducted on the sidelines of a meeting of the Organisation for Economic Cooperation and Development.

"We need to see China stop these actions," he said, adding that "we'll see" whether Biden and Xi are able to meet in person in coming weeks or months.