General Ryder added that US officials are monitoring the object and reviewing "options". He said the balloon - which he described as "manoeuvrable" - poses no military or physical threat to people on the ground.

Although fighter planes were alerted, the US decided not to shoot the object down due to the dangers of falling debris, officials said.

The incident has also revealed as much about domestic politics as it did about as geopolitical rivalries, with Mr Biden's political opponents leading the charge in demanding action against China.

Several Republican lawmakers - as well as former President Donald Trump - have criticised the decision and urged the US to down the balloon.

"Shoot down the balloon," Mr Trump said in a short message on his Truth Social social media platform.

On Twitter, House Speaker Kevin McCarthy said that the balloon incident was "a destabilizing action that must be addressed".

As the situation continues, the Biden administration must now contend with China "hawks" on both sides of the political spectrum.

Montana Democratic Senator Jon Tester, for example, said in a statement that he is "still waiting on real answers" about how the "unacceptable" incident happened.

"I will hold everyone accountable until I get them," the statement said.

Speaking to CBS, a US official described the payload of the balloon - the attached part from which surveillance is carried out - as being as large as two or three school buses. The balloon itself is significantly larger.

Chinese officials have previously publicly expressed interest in the potential military and intelligence-gathering potential of balloons.

"Technological advances have opened a new door for the use of balloons," an article in the military-run Liberation Army Daily said last year.

In 2022, Taiwan's defence ministry said it detected Chinese balloons over its territory.