At the lower end of the estimate, the asteroid is comparable in size to the Eiffel Tower in Paris, France.
The 2018 White House report on the dangers of unidentified asteroids suggests a case that this large could kill untold millions.
A chart comparing the relative size of an asteroid to potential "impact destruction" shows that something measuring between 1,312 to 5,249ft (400m and 1.6km) across can destroy an entire continent.
The report states: “Even small NEOs can have significant destructive effects.
"For example, on February 15, 2013, an asteroid approximately 20 meters in size created an air flow near Chelyabinsk, Russia, with approximately 20 to 30 times more energy than the first atomic bombs issued.