The White House sought on Tuesday to take the air out of an escalating diplomatic crisis with Beijing, saying that preliminary evidence suggests three unidentified aerial objects shot down by US jets were not involved in a broader Chinese spy balloon programme.

The United States has been in a state of alarm since a huge white balloon from China was spotted tracking over a series of top-secret nuclear weapons sites, before being shot down just off the east coast on February 4.

In the wake of the incident, the US military adjusted radar settings to detect smaller objects and promptly discovered three more unidentified craft that President Joe Biden ordered shot down — one over Alaska, another over Canada and the third over Lake Huron off Michigan.

US authorities “haven’t seen any indication or anything that points specifically to the idea that these three objects were part of [China’s] spy balloon programme or that they were definitely involved in external intelligence”, National Security Council spokesman John Kirby said.

With Congress, the media and the public speculating over everything from a coordinated Chinese spying offensive to aliens, officials are now stressing that the three new objects appear to be neither Chinese nor involved in spying.

Kirby said they “could be balloons that were simply tied to commercial or research entities and therefore benign.” That “could emerge as a leading explanation here”, he said.

Beijing denies it uses spy balloons and says the huge craft shot down off the coast on February 4 was for weather research, while another spotted over South America was for pilot training.

On Monday, Chinese authorities upped the ante by accusing Washington of sending its own spy balloons over their territory — something US officials deny.

The spat has already inflicted diplomatic damage between the rival superpowers, with Secretary of State Antony Blinken abruptly cancelling a rare visit to Beijing.

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Kirby stressed that China is running a “well-funded, deliberate programme” to use high-altitude, hard-to-detect balloons for spying on the United States and other countries.

But whether the three latest objects downed were part of that will not be definitively known until the debris is analysed — and that is taking more time than US authorities would like.

“It will certainly help us hone in on that if and when we can get the debris,” Kirby said.

But due to “pretty tough” weather and geographical conditions in all three cases, “we’re recognising that it could be some time before we locate and recover the debris”, Kirby said.

“We haven’t found them yet.”

The next question will be how to calibrate the military’s radar shield.

If the three destroyed objects turn out to have been private or otherwise non-hostile aircraft, then the Pentagon will have to decide whether it should be responding so aggressively after every sighting.

An inter-agency security review is underway, Kirby said, and in the meantime, there’s no reason to expect a similar rate of drama.

“I never said there was some sort of blanket policy, that we’re just going to shoot things out of the sky.”