US president Joe Biden said the country was 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 procedures after the United States shot down the Chinese balloon, as well as three other objects that Mr Biden said the US now believed were most likely “benign” objects launched by private companies or research institutions.

Mr 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.

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

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

Secretary of state Anthony Blinken postponed his first planned trip to China as the balloon was flying over the US, and a new meeting with his Chinese counterpart has yet to be scheduled.

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

[ Balloons, aliens, Chinese espionage: US struggles to explain aerial encounters ]

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

The Chinese balloon has escalated tensions between the US and China.

Mr Blinken travelled on Thursday to the Munich Security Conference and there was speculation he might use the opportunity to meet top Chinese foreign policy official Wang Yi, who will also be attending the conference.

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 US. – AP