A US fighter jet shot down an unidentified object drifting high over Alaska on Friday, the White House said, just six days after the downing of an alleged Chinese spy balloon sparked a fresh diplomatic rift with Beijing.

White House National Security Council spokesman John Kirby said it was unclear what the purpose or origin of the new object was, but said that it was taken down because, floating at 40,000 feet, it was a threat to civil aviation.

"The president ordered the military to down the object," Kirby said.

Questioned about the incident by reporters at the White House, Biden said the shoot-down "was a success."

Kirby said the object was much smaller than a huge Chinese balloon that crossed the United States last week and was shot down by a US fighter jet off the Atlantic coast on Saturday.

It was "roughly the size of a small car," he said.

"We do not know who owns it, whether state owned or corporate owned," he said. "We don't understand the full purpose."

Pentagon spokesman Brigadier General Pat Ryder said an F-22 Raptor used an AIM-9X missile to bring down the object -- the same aircraft and munition used to target the alleged Chinese spy balloon.

The incident took place amid a new alarm over what US officials say is an ongoing program by China to fly surveillance balloons to collect intelligence around the world.

US officials said such balloons have flown over 40 countries, including at least four times previously over United States territory.

The Chinese balloon last week sparked particular concern as it overflew areas where the United States keeps nuclear missiles in underground silos and bases strategic bombers.

The incident led US Secretary of State Antony Blinken to cancel an imminent trip to Beijing that had been long in planning and aimed at improving communications between the two rival superpowers.

Kirby said the new object was detected late Thursday, and shot down Friday afternoon Washington time.

It went down in northern Alaska near the Canadian border and fell over a frozen body of water, making recovery feasible, Kirby said.

"We do expect to be able to recover the debris," he said.

Biden ordered the shoot-down because at the altitude it was flying, Kirby said, the object posed "a reasonable threat" to civil aviation.

Kirby said the US military sent a plane to observe the object before it was taken down and "the pilot's assessment was that this was not manned."

The Chinese surveillance balloon had clear abilities to propel and maneuver itself, he noted.

It "was clearly for intelligence surveillance and inconsistent with the equipment onboard weather balloons," a senior State Department official said Thursday.

"It had multiple antennas to include an array likely capable of collecting and geo-locating communications," the official.

The official also tied the balloon to China's People's Liberation Army, without saying directly that it had been deployed by the PLA.

The Pentagon's Ryder said the US recovery teams have finished mapping the debris field from the downed Chinese balloon and "are in the process of searching for and identifying debris on the ocean floor."

"Debris that's been recovered so far is being loaded on the vessels, taken ashore, catalogued and then moved onwards to labs for subsequent analysis," he added.

Beijing has rejected US allegations that it sent the balloon to spy on the United States, and said it had simply drifted by accident into US airspace.

But since Saturday China has rejected an overture by US Defense Secretary Lloyd Austin to speak by phone about the issue.

"The US insisted on using force to attack the airship, which seriously violated international practice and sets a bad precedent," the Chinese defense ministry said in a statement.