Pentagon says it is monitoring Chinese spy balloon spotted flying over US

The Pentagon has said it is tracking a Chinese spy balloon flying over the US but decided against shooting it down for safety reasons.

Defence officials said the balloon had been watched since it entered US airspace at high altitude a couple of days ago. It has been monitored by several methods including crewed aircraft, and has most recently been tracked crossing Montana, where the US has silo-based nuclear missiles.

As a precaution, flights from Billings Logan airport were suspended on Wednesday.

Related: Spy balloons: what are they and why are they still being used?

The Chinese government has not confirmed if it owns the balloon, and state-backed media have used the incident to taunt the US.

“The balloon itself is a big target,” the state-backed nationalistic tabloid the Global Times wrote in English on Twitter, which is banned in China. “If balloons from other countries could really enter continental US smoothly, or even enter the sky over certain states, it only proves that the US’s air defence system is completely a decoration and cannot be trusted.”

On Friday afternoon, China Daily said the spy balloon claims were a lie. “To spy on the US with a balloon, one must both fall far behind to use a 1940s technology and be advanced enough to control its flight across the ocean. Those fabricating the lie are only exposing their ignorance,” it said.

After the Pentagon’s announcement, Canada’s national defence department said it too had detected a high-altitude surveillance balloon and was “monitoring a potential second incident”. US officials said earlier that the balloon had travelled over part of Canada on its way to Montana.

Canada’s defence authorities made clear there was no public danger, adding: “Canada’s intelligence agencies are working with American partners and continue to take all necessary measures to safeguard Canada’s sensitive information from foreign intelligence threats.”

The Pentagon said: “The balloon is currently traveling at an altitude well above commercial air traffic and does not present a military or physical threat to people on the ground. Instances of this kind of balloon activity have been observed previously over the past several years. Once the balloon was detected, the US government acted immediately to protect against the collection of sensitive information.”

Related: US general’s ‘gut’ feeling of war with China sparks alarm over predictions

The incident comes just before the US secretary of state, Antony Blinken, was expected to visit China this weekend to meet the president, Xi Jinping. The trip has not been formally announced, but Beijing and Washington have been talking about his imminent arrival.

Blinken’s visit, amid bilateral attempts to repair relations, has also coincided with other points of friction. Beijing this week strenuously objected to a deal between the Philippines and the US in which Manila has granted the US expanded access to its military bases. Under the deal, the US will have additional access to Philippine bases for joint training, storing equipment and supplies, and building facilities, though not to establish a permanent presence.

Analysts have said the deal fills a crucial gap in US military positioning in the region, enhancing its ability to monitor the South China Sea and around Taiwan. Both are significant areas of concern regarding Chinese military activities. On Thursday, China’s ministry of foreign affairs spokesperson accused the US of “exacerbating regional tension and jeopardising regional peace and stability” with the deal.

There was intense speculation among analysts on Friday about how China might explain the spy balloon. A senior US defence official said the US had “engaged” with Chinese officials through multiple channels about the seriousness of the matter.

A spokesperson for China’s ministry of foreign affairs said Beijing was “verifying” the situation. “I would like to emphasise that until the facts are clarified, speculation and hype will not be helpful to the proper resolution of the issue,” Mao Ning told a daily press conference.

Mao said China had no intention of violating the territory and airspace of any country, and that the government hoped to handle the matter with the US “calmly”, according to state media.

Pentagon officials said there was “high confidence” that the balloon was Chinese, and that Joe Biden had been briefed on the situation. The president asked for military options, but it was decided there was too great a danger of debris harming people on the ground were it to be shot down.

It was also judged that although it was flying over sensitive nuclear sites in Montana, it did not appear to be gathering any intelligence that could not be collected from satellites.

Montana is home to one of the nation’s three nuclear missile silo fields at Malmstrom air force base. All air traffic was halted at Montana’s Billings Logan international airport from 1.30pm to 3.30pm on Wednesday as the military readied fighter jets and provided options to the White House.

Congressional leaders were briefed on Thursday afternoon. The House speaker, Kevin McCarthy, later tweeted: “China’s brazen disregard for US sovereignty is a destabilising action that must be addressed.”

The Montana governor, Greg Gianforte, said he was briefed on Wednesday about the situation after the state’s national guard was notified of an ongoing military operation taking place in its airspace.

The object first flew over Alaska’s Aleutian Islands and Canada before appearing over Billings on Wednesday, officials said.

Military experts say the use of high-altitude balloons is likely to increase. They are cheaper than spy satellites, are hard to spot by radar and difficult to shoot down, sometimes lingering for days after they have been punctured. They can “steer” by changing altitudes, using computers to calculate how to use winds going in different directions at different layers of the atmosphere. As well as surveillance, they could also carry bombs in times of conflict.

In 2019, the US military used up to 25 experimental solar-powered high-altitude balloons to conduct wide-area surveillance tests across six midwestern states. The balloons were equipped with hi-tech radars designed to simultaneously track many individual vehicles day or night, through any kind of weather, and were intended to be used to monitor drug trafficking and potential homeland security threats.

Tensions with China are high on issues ranging from Taiwan and the South China Sea to human rights in China’s western Xinjiang region and the clampdown on democracy activists in Hong Kong. Other irritants are China’s tacit support for Russia’s invasion of Ukraine, its refusal to rein in North Korea’s expanding ballistic missile programme, and ongoing disputes over trade and technology.

Some Montana residents reported seeing an unusual object in the sky during the airport shutdown, but it is not clear if what they were seeing was the balloon.

From an office window in Billings, Chase Doak said he saw a “big white circle in the sky” that he said was too small to be the moon. He took some photos, then ran home to get a camera with a stronger lens and took more photos and video. He could see it for about 45 minutes and it appeared stationary, but Doak said the video suggested it was moving slowly.

“I thought maybe it was a legitimate UFO,” he said. “So I wanted to make sure I documented it and took as many photos as I could.”