Biden told reporters on Thursday that intelligence officials are still assessing the objects, but there was no evidence that they were linked to an alleged Chinese spy balloon that US forces downed off the coast of South Carolina after it had traversed the country.

“The intelligence community’s current assessment is that these three objects were most likely balloons tied to private companies, recreation or research institutions studying weather or conducting other scientific research,” the president said.

The objects were found and shot down over the US and Canada in the past week, but the two countries initially said they did not know the exact nature or origin of the aircraft, sparking questions and concern from the public and policymakers.

The incidents came days after US forces on February 4 shot down the alleged Chinese spy balloon, whose flight Washington called an “unacceptable” violation of its sovereignty.

Beijing, which insisted that the aircraft was a weather research balloon that accidentally strayed into US airspace, condemned the decision to take it down.

While US officials have stressed that there was no proven links between the subsequent aircraft and China, they said it was possible Washington and Ottawa were finding more aerial objects after the Chinese balloon put them on heightened alert.

Biden reiterated that assessment on Thursday, saying the objects were found after American forces further scrutinised the country’s airspace and adjusted radar systems to “pick up more slow-moving” aircraft.

Biden added that he authorised US military aircraft to shoot down the objects “out of an abundance of caution” because they flew within the range of civilian air traffic.

White House national security spokesperson John Kirby previously said the objects were not manned, did not appear to send communication signals and did not pose a threat to people on the ground.

The objects and the mystery surrounding them garnered so much public attention and speculation that on Monday the White House ruled out aliens as an explanation for the aircraft, saying there was no indication of “extraterrestrial activity” associated with the takedowns.

China tensions

Biden addressed the Chinese balloon controversy and tried to justify the decision to wait for days before shooting it down, after facing Republican criticism over the delay.

Biden, a Democrat, said he ordered US forces to take down the balloon “as soon as it would be safe to do so”.

“The military advised against shooting it down over land because of the sheer size of it,” he said.  “It was the size of multiple school buses, and it posed a risk to people on the ground if it were shot down where people lived.”

Instead, Biden said the military tracked and monitored the balloon as it crossed the country to analyse its capabilities while protecting sensitive sites against data collection.

The incident inflamed tensions between the two superpowers, which are already locked in an intensifying rivalry.

Biden stressed the importance of communication with Beijing, saying he expects to speak with Chinese President Xi Jinping in the future without providing a specific timeframe.

“We’re also continuing to engage with China as we have throughout the past two weeks,” Biden said. “As I’ve said since the beginning of my administration: We seek competition, not conflict with China. We’re not looking for a new Cold War.”

Still, the US president added that he makes no apologies about shooting down the balloon.

Earlier on Friday, Beijing urged Washington to work to “avoid misunderstanding and miscalculation” with China.

“The unintended entry of the Chinese civilian airship into US airspace is an entirely unexpected, isolated incident,” Wang Wenbin, foreign ministry spokesman, said during a news briefing. “It is, however, a test for the US side’s capability to properly manage [a] crisis and sincerity about stabilising relations with China.”

On Monday, Beijing said Washington had flown high-altitude balloons over its territory without permission 10 times in the past year, accusations that US officials repeatedly denied.