Beijing admitted ownership of the 'airship' and said it veered off course due to the winds

US Secretary of State Antony Blinken on Friday scrapped a long-planned Beijing trip aimed at easing escalating tensions between the two superpowers after the Pentagon said that China sent a spy balloon over the United States.

Moments before the decision, China issued a late-night statement voicing regret over what it called an accident with a civilian airship but the United States was not impressed.

Blinken, who has faced intense pressure over the trip from the rival Republican Party, decided to postpone his two-day visit starting Sunday, which would have been the first by a top US diplomat since October 2018, a US official said.

The official said the United States was "confident" of preserving communication with China despite Blinken's cancellation, and that the visit would be rescheduled once conditions are "right."

The Pentagon said Thursday it was tracking the balloon which flew far above the western state of Montana and decided for safety reasons not to shoot it down.

After initial hesitation, Beijing admitted ownership of the "airship" and said it veered off course due to the winds.

"The airship is from China. It is a civilian airship used for research, mainly meteorological, purposes," said the statement attributed to a foreign ministry spokesperson.

"The Chinese side regrets the unintended entry of the airship into US airspace due to force majeure," it said, using the legal term for an act outside of human control.

"The Chinese side will continue communicating with the US side and properly handle this unexpected situation."

Republican lawmakers quickly pounced on the incident, casting President Joe Biden -- who has largely preserved and at times expanded his Republican predecessor Donald Trump's hawkish policies on China -- as weak.

"President Biden should stop coddling and appeasing the Chinese communists. Bring the balloon down now and exploit its tech package, which could be an intelligence bonanza," tweeted Senator Tom Cotton, a prominent hardliner who had urged Blinken to call off his trip.

A senior defence official said that Biden had asked for military options but that the Pentagon believed shooting the object down would put people on the ground at risk from debris.

The balloon has "limited additive value from an intelligence collection perspective," the official told reporters on condition of anonymity.

But the official said it was clearly a balloon meant for surveillance.

The United States is also widely believed to spy on China, although generally with more advanced technology than balloons.

The northwestern United States is home to sensitive airbases and nuclear weapons in underground silos.

The Pentagon said that fighter jets were flown to examine the balloon. Canada also said it had tracked the balloon.

Pentagon spokesman Pat Ryder said that, as of Thursday, the balloon was "travelling at an altitude well above commercial air traffic."

"It does not present a military or physical threat to people on the ground," Ryder said in a statement.

Defense Secretary Lloyd Austin, who was visiting the Philippines, held discussions Wednesday with top Pentagon officials after Biden asked for options, the defence official said.

In the Philippines, Austin agreed to expand the US military presence, weeks after a separate troop deal with another regional ally, Japan.

The US military moves show that the United States is preparing for potential conflict over Taiwan, the self-governing democracy China claims as its own, despite diplomatic efforts.

Biden held a surprisingly cordial meeting in November with Chinese President Xi Jinping on the sidelines of a summit in Bali, where they agreed to send Blinken to Beijing.

Blinken had described China as a leading competitor but said last month that his trip was intended to set "guardrails" to prevent tensions from escalating into conflict.

A senior US military officer recently told his forces to be ready for war with China after Taiwan's elections next year.

"I hope I am wrong. My gut tells me we will fight in 2025," Air Mobility Command chief General Mike Minihan wrote in a memo, saying that US elections in 2024 would also "offer Xi a distracted America."

Blinken has said that Xi has been speeding up his timeframe to "reunify" with Taiwan, to which the United States sells weapons.

But Austin, while accusing China of trying to "establish a new normal" on Taiwan, said last month he doubted an invasion is "imminent."