WASHINGTON — The U.S. is tracking a suspected Chinese surveillance balloon that has been spotted over U.S. airspace for a couple days, but the Pentagon decided not to shoot it down due to risks of harm for people on the ground, officials said Thursday. The discovery of the balloon puts a further strain on U.S.-China relations at a time of heightened tensions.

A senior defense official told Pentagon reporters that the U.S. has “very high confidence” it is a Chinese high-altitude balloon and it was flying over sensitive sites to collect information. One of the places the balloon was spotted was Montana, which is home to one of the nation’s three nuclear missile silo fields at Malmstrom Air Force Base. The official spoke on condition of anonymity to discuss sensitive information.

Brig. Gen. Patrick Ryder, Pentagon press secretary, provided a brief statement on the issue, saying the government continues to track the balloon. He said it 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.”

He said similar balloon activity has been seen in the past several years. He added that the U.S. took steps to ensure it did not collect sensitive information.

The defense official said the U.S. has “engaged” Chinese officials through multiple channels and communicated the seriousness of the matter.

Blinken Headed to China

The incident comes as Secretary of State Antony Blinken was supposed to make his first trip to Beijing, expected this weekend, to try to find some common ground. Although the trip has not been formally announced, both Beijing and Washington have been talking about his imminent arrival.

It was not immediately clear if the discovery of the balloon would impact Blinken’s travel plans.

The senior defense official said the U.S. did get fighter jets, including F-22s, ready to shoot down the balloon if ordered to by the White House. The Pentagon ultimately recommended against it, noting that even as the balloon was over a sparsely populated area of Montana, its size would create a debris field large enough that it could have put people at risk.

The official would not specify the size of the balloon, but said it was large enough that despite its high altitude, commercial pilots could see it. All air traffic at the Billings, Montana, Logan International Airport was placed on a temporary ground stop Wednesday as the military provided options to the White House. A photograph of a large white balloon lingering over the area was captured by the Billings Gazette, but the Pentagon would not confirm if that was the surveillance balloon.

The official said what concerned them about this launch was the altitude the balloon was flying at and the length of time it lingered over a location, without providing specifics.

Tensions High With China

Tensions with China are particularly high on numerous 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. Not least on that list of irritants are China’s tacit support for Russia’s invasion of Ukraine, its refusal to rein in North Korea’s expanding ballistic missile program and ongoing disputes over trade and technology.

On Tuesday, Taiwan scrambled fighter jets, put its navy on alert and activated missile systems in response to nearby operations by 34 Chinese military aircraft and nine warships that are part Beijing’s strategy to unsettle and intimidate the self-governing island democracy.

Twenty of those aircraft crossed the central line in the Taiwan Strait that has long been an unofficial buffer zone between the two sides, which separated during a civil war in 1949.

Beijing has also increased preparations for a potential blockade or military action against Taiwan, which has stirred increasing concern among military leaders, diplomats and elected officials in the U.S., Taiwan’s key ally.

The surveillance balloon was first reported by NBC News.