NASA is monitoring a 100ft (30m) wide asteroid set to pass closer to the Earth than the communication satellites that ring the planet.
2013 TX68 could fly within 11,000 miles (17,700km) of Earth on 5 March, roughly 1/20th the distance from Earth to the moon and about half as far as most satellites.
However, the space agency stresses there is no chance of a collision.
The uncertainty about its exact path of the asteroid means it could still pass as far away as nine million miles during its flyby.
It was visible for just three days during its last approach before it disappeared into daytime skies and could no longer be tracked.
“It will be hard to predict where to look for it,” Paul Chodas, who manages the NASA’s Near-Earth Objects Studies office, said in a statement.
NASA said there is a one-in-250 million chance of an impact during the asteroid’s next pass on 28 September, 2017.
“The possibilities of collision on any of the three future flyby dates are far too small to be of any real concern,” said Mr Chodas.
The asteroid is about twice the size of the one that exploded over Chelyabinsk, Russia, in 2013.
That blast shattered glass and destroyed buildings, injuring more than 1,000 people.