A suspected Chinese spy balloon has been flying over the United States for a few days, and senior US officials have advised President Joe Biden against shooting it down for fear the debris could pose a safety threat.

Washington has been tracking the balloon since it entered US airspace two days ago, including by observing it with manned military aircraft.

“We are confident that this high-altitude surveillance balloon belongs to the [People’s Republic of China],” a senior defence official was quoted as saying by CNN.

“Instances of this activity have been observed over the past several years, including prior to this administration.”

China and the US – the world’s two largest economies – have experienced tensions of late, clashing over Taiwan and China’s human rights record and its military activity in the South China Sea.

Officials declined to say how high it was flying but acknowledged it was operating above civilian air traffic and below outer space.

Senior US military leaders considered shooting the balloon down over Montana but eventually recommended against it because of the potential safety risk from debris.

President Joe Biden has been briefed on the balloon’s movements and requested options on how to deal with it, according to another senior administration official.

US officials brought up the issue with their Chinese counterparts.

“We have communicated to them the seriousness with which we take this issue,” the official said.

Spy balloons have flown over the US several times in recent years, but this balloon appeared to be lingering longer than in previous instances.

“Currently, we assess that this balloon has limited additive value from an intelligence collection perspective but we are taking steps nevertheless to protect against foreign intelligence collection of sensitive information,” the official said.

– with AAP