A 40m-long chunk of rock hurtling through space will pass closer to the Earth than any other near miss on record, Nasa is expected to say.
Scientists at the space agency are expected to reveal the reassuring news for Earthlings at a news conference on Thursday.
Their calculations predict Asteroid 2012 DA14 will whistle past Earth on February 15 closer than the orbit of some weather and communications satellites, speeding by at a distance of 17,000 miles (27,400km).
That would be the planet's closest shave with an identified flying object since records began.
Asteroids and meteorites that have come closer than that have ended up colliding with the planet but this one is not thought to be a danger to either us or satellites.
It was discovered by a Spanish dentist turned amateur asteroid spotter. He is part of a team of enthusiasts who in turn are part of an army of asteroid watchers vital to Nasa's early warning system.
Former space shuttle astronaut Tom Jones told Sky News there are thought to be a million asteroids out there as big as 2012 DA14.
They are called 'city killers' because they would be able to wipe out a metropolitan area should they hit the planet. Nasa is thought to have tabs on only 1% of them.
One struck a remote part of Russia in 1908 and flattened vast areas of forest in what became known as the Tunguska incident.
So-called 'planet killers' are far more dangerous and hundreds have been observed. A 'planet killer' is widely believed to have wiped out the dinosaurs.