President Joe Biden said the United States is developing “sharper rules” to track, monitor and potentially shoot down unknown aerial objects,

following three weeks of high-stakes drama sparked by the discovery of a suspected Chinese spy balloon transiting much of the country.

The president has directed national security adviser Jake Sullivan to lead an “interagency team” to review US procedures after it shot down the Chinese balloon, as well as three other objects that Biden said they now believe were most likely “benign” objects that were launched by private companies or research institutions.

Biden said he hoped the new rules would help “distinguish between those that are likely to pose safety and security risks that necessitate action and those that do not.”

“Make no mistake, if any object presents a threat to the safety and security of the American people I will take it down,” he added.

The downing of the Chinese surveillance craft was the first known peacetime shootdown of an unauthorised object in US airspace – a feat repeated three times a week later.

Biden sharply criticised China’s surveillance program, saying the “violation of our sovereignty is unacceptable,” but said he looks to maintain open lines of communication with Beijing.

“I expect to be speaking with President Xi and I hope we can get to the bottom of this,” Biden said, adding, “But I make no apologies for taking down that balloon.”

Biden said the rules would remain classified so as not to “give a roadmap to our enemies to try to evade our defenses.”

Biden had remained largely silent on the objects downed Friday off the coast of Alaska, Saturday over Canada and Sunday over Lake Huron.

On Monday, the White House announced earnestly there was no indication of “aliens or extraterrestrial activity.”

By Wednesday, US officials said they were still working to locate the wreckage from the objects, but that they expected all three to be unrelated to surveillance efforts.

Still unaddressed are questions about the original balloon, including what spying capabilities it had and whether it was transmitting signals as it flew over sensitive military sites in the United States.