Joe Biden has broken his silence on unknown aerial objects shot down over North America during the past week, assessing that they were “most likely” operated by private companies or research institutions rather than China.

The US president’s tentative conclusion is likely to fuel criticism that his orders to take down the objects were an overreaction amid political pressure over the discovery of a suspected Chinese spy balloon that transited much of the country.

Biden spoke for eight minutes at the Eisenhower executive office building on Thursday after Republicans and some Democrats expressed concerns that his unwillingness to comment on the issue could allow conspiracy theories to thrive.

“We don’t yet know exactly what these three objects were but nothing right now suggests they were related to China’s spy balloon program or that they were surveillance vehicles from any other country,” the president told reporters, against a backdrop of flags and the presidential seal.

“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.”

Earlier this month an American fighter jet downed a balloon sent by the Chinese government off the coast of South Carolina. The incident prompted accusations from Republicans that Biden had been too slow to react and should have shot it down before it passed over the continental US.

When three additional unidentified objects were spotted on Friday off the coast of Alaska, on Saturday over Canada and on Sunday over Lake Huron, Biden was quick to order that they be taken down.

But on Thursday, with efforts to relocate the wreckage hampered by weather, he acknowledged that many objects are sent up by countries, companies and research organisations for reasons that are “not nefarious”, including legitimate scientific research.

“I want to be clear,” Biden said. “We don’t have any evidence that there has been a sudden increase in the number of objects in the sky. We’re now just seeing more of them partially because the steps we’ve taken to increase our radars.”

The president, who has directed national security adviser Jake Sullivan to lead an “interagency team” to review procedures, said the US is developing “sharper rules” to track, monitor and potentially shoot down unknown aerial objects.

These rules would help “distinguish between those that are likely to pose safety and security risks that necessitate action and those that do not,” he added. “Make no mistake, if any object presents a threat to the safety and security of the American people I will take it down.”

The downing of the Chinese surveillance craft was the first known peacetime shoot down of an unauthorised object in US airspace and continues to send out diplomatic ripples.

The White House national security council has said the balloon had the ability to collect communications and that China has previously flown similar surveillance balloons over dozens of countries on multiple continents, including some of the US’s closest allies.

The US blacklisted six Chinese entities it said were linked to Beijing’s aerospace programmes.

China has denied that the balloon was a surveillance airship. Wang Wenbin, a foreign ministry spokesperson, told a press conference that the balloon’s entry into US airspace was “an unintended, unexpected and isolated event”, adding: “China has repeatedly communicated this to the US side, yet the US overreacted by abusing the use of force and escalating the situation.

“It also used the incident as an excuse to impose illegal sanctions over Chinese companies and institutions. China is strongly opposed to this and will take countermeasures in accordance with law against relevant US entities that have undermined China’s sovereignty and security to firmly safeguard China’s sovereignty and legitimate rights and interests.”

US relations with China have been tested over the last year due to tensions over cybersecurity, competition in the technology sector, the looming threat to Taiwan and China’s failure to condemn the Russian invasion of Ukraine.

On Thursday Biden criticised China’s surveillance programme, saying the “violation of our sovereignty is unacceptable,” but said he looks to maintain open lines of communication with Beijing. “We’re not looking for a new cold war.”

Secretary of state Antony 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,” Biden said. “But I make no apologies for taking down that balloon.”

Senators from both sides of the aisle have complained about being denied detailed information. John Cornyn, a Republican senator for Texas, told the Politico website that the White House was “creating a bigger problem for themselves by the lack of transparency because people’s minds, their imaginations begin to run wild. I think they’re behind the curve on this and they really need to be more transparent.”

On Monday, just to be sure, the White House felt compelled to announce that there was no indication of “aliens or extraterrestrial activity”.