Secretary of State Antony Blinken will delay his trip to Beijing after the military spotted a suspected spy balloon drifting over Montana, a US official has said.
Mr Blinken did not want to blow the situation out of proportion by cancelling his visit, but also did not want the balloon incident to dominate his meetings with Chinese officials, a high-ranking US official said in a call with reporters.
"I spoke this morning with Director of the CCP [Chinese Communist Party] Central Foreign Affairs Office Wang Yi to convey that, in light of China's unacceptable action, I am postponing my planned travel this weekend to China," Mr Blinken said.
He added that the US had been in repeated communications with Chinese officials over the issue.
The postponement of Mr Blinken's trip, agreed to in November, will be a blow to those on both sides who saw it as an overdue opportunity to stabilise an increasingly fractious relationship.
China on Friday said the high-altitude balloon that the Pentagon was tracking over US airspace is being used for weather research and had been inadvertently blown off course.
The claim came after the Pentagon on Thursday said it was monitoring the balloon as a potential spying vessel. The incident has heaped fresh strain on already tense relations between Beijing and Washington.
It was spotted on the Canadian border earlier in the week and the balloon later entered US airspace in the state of Montana.
Montana is one of the largest states in the US and also one of the least populated. Malmstrom Air Force Base in Cascade County is home to one of three active nuclear missile silos in the country.
The US “detected and is tracking a high-altitude surveillance balloon that is over the continental United States right now”, Pentagon spokesman Brig Gen Pat Ryder said on Thursday.
Malmstrom Air Force Base, Montana - in pictures
The Pentagon on Friday confirmed that the balloon, which is currently flying at an altitude of more than 18,000 metres, is travelling “eastward” and presently over the “centre of the continental US".
Brig Gen Ryder would not go into any specifics a the balloon, but acknowledge it was fairly large.
The US decided not to shoot down the balloon, which was potentially flying over sensitive sites, because of concerns that falling debris could hurt people on the ground.
“Once the balloon was detected, the US government acted immediately to protect against the collection of sensitive information,” Brig Gen Ryder said. Similar balloon sightings have occurred in recent years, he added.
In a statement on Friday, China's Ministry of Foreign Affairs said the balloon was civilian airship used mainly for meteorological research.
The ministry said the airship has limited “self-steering” capabilities and had “deviated far from its planned course” because of winds.
“The Chinese side regrets the unintended entry of the airship into US airspace due to force majeure,” the statement said, according to The Associated Press, citing a legal term used to refer to events beyond one’s control.
In response, a US official on Friday said China's statement of regret was "noted", but the presence of the balloon in US airspace is "a clear violation of our sovereignty as well as international law, and it is unacceptable that this has occurred".
“We have concluded that the conditions are not right at this moment for Secretary Blinken to travel to China," the official said.
The official added that there had been hopes for a "broad, substantive agenda" and "constructive engagement" on issues pertaining to the US-China bilateral relationship.
"There is a Chinese high altitude surveillance balloon currently over the United States is a clear and unacceptable violation of US sovereignty and we have made that crystal clear," the official continued.
The official added, however, that: "I'm confident that our channels of communication will remain as important as ever and those channels do remain open."
The sighting comes at a time of high US-China tension over military build-up in Asia as well as intensifying economic and technology competition, though Washington and Beijing have begun to warm up to economic talks.
The US “continues to track and monitor it closely”, Brig Gen Ryder said.
“The balloon is currently travelling at an altitude well above commercial air traffic and does not present a military or physical threat to people on the ground,” he added.