BEIJING --- China said Friday it was ending cooperation with the United States on key issues including climate change -- a move Washington decried as "fundamentally irresponsible" as relations between the two superpowers nosedive over Taiwan.
The damaging rift, which carries significant geostrategic risk, was triggered by Chinese fury over a visit by U.S. House Speaker Nancy Pelosi to Taiwan, which Beijing claims as its territory and has vowed to retake -- by force if necessary.
It has since Thursday encircled the self-ruled, democratic island with a series of huge military drills that have been roundly condemned by the United States and other Western allies.
And Friday saw China's foreign ministry hit back further against the United States, suspending talks and cooperation on multiple agreements -- including on climate change.
The world's two largest polluters last year pledged to work together to accelerate climate action this decade, and vowed to meet regularly to tackle the crisis.
But that deal now looks shaky in light of China's latest move.
"We believe that this is fundamentally irresponsible," National Security Council spokesman John Kirby told reporters in Washington.
"They think they're punishing us... they're actually punishing the whole world," Kirby said, adding that the only way to defuse tensions was for China to halt its "provocative" military exercises.
UN Secretary-General Antonio Guterres warned the two superpowers must continue to work together -- for the world's sake.
"For the secretary-general there is no way to solve the most pressing problems of all the world without an effective dialogue and cooperation between the two countries," his spokesman Stephane Dujarric said.
Taiwan Premier Su Tseng-chang said the "evil neighbour next door" had taken everyone by surprise with its willingness to "arbitrarily jeopardise the busiest waterways in the world" with its military exercises.
'Our motherland is powerful'
Beijing has said its drills will continue until midday Sunday, and Taipei reported that 68 Chinese planes and 13 warships crossed the "median line" that runs down the Taiwan Strait on Friday.
A fighter jet flew over the Chinese island of Pingtan, prompting tourists to snap photos, according to AFP journalists on the scene. A Chinese military vessel sailing through the Taiwan Strait was also visible.
China's drills involved a "conventional missile firepower assault" in waters east of Taiwan, the Chinese military said.
And state broadcaster CCTV reported that Chinese missiles flew directly over Taiwan -- a major escalation if confirmed.
On Pingtan, local tourists proudly extolled Beijing's military might against its much smaller neighbour.
"Our motherland is powerful. We are not afraid of having war with Taiwan, the U.S. or any country in the world," Liu, a 40-year-old tourist from Zhejiang province, told AFP.
"We hope to unify Taiwan soon," he added. "We don't want to start a war, but we are not afraid of others."
Wang, a businesswoman, was more sanguine about prospects for cross-strait ties.
"I hope China can unify Taiwan, but I don't want war," she said. "I hope this issue can be solved in a peaceful way."
The scale and intensity of China's drills have triggered outrage in the United States and other democracies, with the White House summoning China's ambassador to Washington Friday to rebuke him over Beijing's actions.
"The fact is, the speaker's visit was peaceful," U.S. Secretary of State Antony Blinken said after talks with Southeast Asian foreign ministers at an ASEAN summit in Phnom Penh.
"There is no justification for this extreme, disproportionate and escalatory military response," he added.
China's foreign minister countered by warning Washington not to escalate tensions.
"America's habit is to create a problem and then use this problem to achieve its goals. But this approach will not work with China," Wang Yi told a press conference on the summit sidelines.
"We want to issue a warning to the U.S. not to act rashly and not to create a bigger crisis."
Japan has lodged a formal diplomatic complaint against Beijing, with five of China's missiles believed to have landed in its exclusive economic zone.
On Friday, Japan's foreign ministry said China cancelled a planned bilateral meeting on the ASEAN summit sidelines.
And Australia -- which has a troubled relationship with China, its largest trading partner -- condemned the drills as "disproportionate and destabilising".
The manoeuvres are taking place along some of the world's busiest shipping routes, used to disseminate the global supply of vital semiconductors and electronic equipment produced in East Asia.