Washington: An alleged Chinese spy balloon said to be the size of three buses was spotted over the United States' airspace, the Pentagon said.
The development comes days ahead of the Beijing visit of Secretary of State Antony Blinken.
"The United States government has detected and is tracking a high-altitude surveillance balloon that is flying over the continental United States right now," Pentagon Spokesman Brigadier Gen Pat Ryder told reporters here on Thursday.
"NORAD (North American Aerospace Defense Command) continues to track and monitor it closely," he said, adding the balloon was spotted over Montana on Thursday and is said to be the size of three buses.
Once the balloon was detected, the US government acted immediately to protect against the collection of sensitive information, Ryder said.
He said the balloon is travelling at an altitude well above commercial air traffic and does not present a military or physical threat to people on the ground.
US President Joe Biden has been briefed about the incident, a senior defence official said, adding the Pentagon is exploring various options.
Chairman of the Joint Chiefs of Staff Gen Mark Milley and US Northern Command Gen Glen VanHerck have recommended not to "take kinetic action because of the potential risk to the safety and security of people on the ground from the possible debris field, officials said.
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," said a defence official.