CNN  — 

As the US and its Canadian partners continue to monitor a suspected Chinese surveillance balloon floating above the northern United States, one question stands out among the rest: Why hasn’t it been shot down?

Officials have said that the balloon’s path carries it over a “number of sensitive sites” in the US. The balloon – which is the size of three buses – has been seen over Montana, which is home to underground US military intercontinental ballistic missile silos.

US Northern Command is coordinating with NASA to determine the debris field if the balloon were to be shot down, according to a defense official.

But so far, officials have determined that the potential damage of falling debris outweighs the risk of the balloon itself, which they said does not have the ability to bring in more intelligence than spy satellites in low Earth orbit, which China already uses.

“Why not shoot it down? We have to do the risk-reward here,” a senior defense official said on Thursday. “So the first question is, does it pose a threat, a physical kinetic threat, to individuals in the United States in the US homeland? Our assessment is it does not. Does it pose a threat to civilian aviation? Our assessment is it does not. Does it pose a significantly enhanced threat on the intelligence side? Our best assessment right now is that it does not. So given that profile, we assess the risk of downing it, even if the probability is low in a sparsely populated area of the debris falling and hurting someone or damaging property, that it wasn’t worth it.”

A US official added on Friday to CNN: “This isn’t like ‘Top Gun’ where it just explodes and doesn’t go anywhere. It’s large and it’s metal, it would put hundreds of Americans at risk.”

President Joe Biden was briefed on the balloon’s movements and requested options from his military advisers. And while there was consideration to down the balloon while it was over Montana, the advice was to ultimately not to. The Biden administration acted “immediately” to protect against the collection of sensitive intelligence, an official said on Thursday.

But that’s not to say that it couldn’t be shot down eventually; the senior defense official said on Thursday that the US has “options to deal with this balloon” if the risk it poses changes.

“We have communicated to (Chinese officials) the seriousness with which we take this issue. … But we have made clear we will do whatever is necessary to protect our people and our homeland,” the official said.

Chinese officials called the balloon a “civilian airship used for research, mainly meteorological, purposes,” which “deviated far from its planned course.”

US Secretary of State Antony Blinken postponed his upcoming trip to China in response to the balloon sighting, according to two US officials. The postponement marks a significant new phase in the tensions between Washington and Beijing.

A US official said there were similar incidents with suspected Chinese surveillance balloons over Hawaii and Guam in recent years. On Thursday, a senior defense official said, “Instances of this activity have been observed over the past several years, including prior to this administration.”

This story has been updated with additional details.