The United States (US) is tracking a suspected Chinese surveillance balloon that has been spotted flying over sensitive sites in recent days.
Defence officials said they were confident the "high-altitude surveillance balloon" belonged to China.
It was most recently seen above the western state of Montana, reports BBC.
But military leaders decided against shooting it down as there were concerns over the danger of falling debris.
China has not yet commented. US President Joe Biden has been briefed on the situation.
According to US officials, the object flew over Alaska's Aleutian Islands and through Canada before appearing over the city of Billings in Montana on Wednesday, officials said.
A senior defence official said the government prepared fighter jets, including F-22s, in case the White House ordered the object to be shot down.
Top military leaders, including Defence Secretary Lloyd Austin and General Mark Milley, chairman of the US Joint Chiefs of Staff, met on Wednesday to assess the threat.
But they advised against taking "kinetic action" against the balloon because of the danger falling debris would pose to people on the ground.
Montana, a sparsely populated western state, is home to one of only three nuclear missile silo fields in the country, at Malmstrom Air Force Base, and officials said the apparent spy craft was flying over sensitive sites to collect information, said the BBC report.
Bd-pratidin English/Golam Rosul
