US officials said they first detected the balloon on January 28 when it entered US airspace near the Aleutian Islands. The balloon traversed Alaska,Canada and then re-entered US airspace over Idaho.

The flight had intelligence value to the US as it allowed officials to study and scrutinise the balloon and its equipment along the way,a defence official said. The US also took steps to mitigate the balloon’s intelligence gathering,the official said.

China had insisted that the balloon was not being used for surveillance,claiming it was simply a weather research “airship” that had blown off course.

“It is a civilian airship used for research,mainly meteorological,purposes,” a Chinese ministry spokesperson said in a statement.

“Affected by the westerlies and with limited self-steering capability,the airship deviated far from its planned course. The Chinese side regrets the unintended entry of the airship into US airspace due to force majeure.”

However,the US rejected this explanation,noting that the balloon had been floating over sensitive military sites in Montana,a western US state that has about 150 intercontinental ballistic missile silos,before moving eastward.

In a statement on Saturday after the balloon was shot down,Secretary of Defence Lloyd Austin said it “was being used by the PRC in an attempt to surveil strategic sites in the continental United States”,which he said was “an unacceptable violation of our sovereignty”.

Austin also confirmed that Biden had ordered that the surveillance balloon be taken “down as soon as the mission could be accomplished without undue risk to American lives under the balloon’s path”.

“After careful analysis,US military commanders had determined downing the balloon while over land posed an undue risk to people across a wide area due to the size and altitude of the balloon and its surveillance payload,” he said.

The balloon was spotted hovering above Montana earlier this week. On Friday night,the Pentagon issued a statement saying that a second balloon had been detected “transiting Latin America”,but did not say where in the vast region – comprising countries as far north as Mexico and as far south at Argentina – it was located.

The discovery of the first balloon alarmed US officials and prompted widespread calls to immediately take it down,including from former president Donald Trump,former secretary of state Mike Pompeo,former UN ambassador Nikki Haley and far-right politicians such as Marjorie Taylor Greene.

Australian Defence Minister Richard Marles,who was in Washington to discuss the AUKUS pact with Austin,also weighed in,noting that the matter had raised “a lot of questions” and “we’ll await those answers from China”.

Critics had earlier accused Biden of being too soft and questioned why he was taking so long to act. Republican Congressman Mike Gallagher,for instance,who chairs the Select Committee on China in the US Congress,had described it as “embarrassing and unfathomable” that the balloon had not been shot down sooner.

“If this were an American asset over Chinese airspace,do you think they’d hesitate for one second to shoot that down?” he said.

US House Speaker Kevin McCarthy had said in a tweet that “China’s brazen disregard for US sovereignty is a destabilising action that must be addressed”. He has requested a briefing with the so-called Gang of Eight – a reference to the eight leaders within the US Congress who are briefed on classified intelligence matters.

Blinken’s trip would have made him the first US Secretary of State to sit down with Xi Jinping in nearly six years and the first of Biden’s cabinet secretaries to visit China. It was meant to be a significant diplomatic moment,following up on Biden’s meeting with the Chinese President last year. Several sensitive issues were on the agenda,including Taiwan and China’s relationship with Russia as the war in Ukraine continues.

However,on Friday morning,Blinken told China’s top foreign policy official Wang Yi that the balloon’s course was a violation of sovereignty and “unacceptable”.

“Any country that has its airspace violated in this way I think would respond similarly,” Blinken later said at a press conference. “And I can only imagine what the reaction would be in China if they were on the other end.”

He said he was open to rescheduling his visit at “an appropriate time” but the priority for now was to get the balloon out of American skies.

“In the meantime,the United States will continue to maintain open lines of communication with China,including to address this ongoing incident,” he said.

“Indeed,that’s why we need direct and regular communications in the first place. And that’s why it’s critical that such lines remain open at all times,to help avoid miscalculation,and conflict.”

With wires

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