But for those fearing Armageddon, do not be alarmed - the chances of a catastrophic collision are just one in 909,000.
Asteroid 2003 QQ47 will be closely monitored over the next two months. Its potential strike date is 21 March 2014, but astronomers say any risk of impact is likely to decrease as further data is gathered.
On impact, it could have the effect of 20 million Hiroshima atomic bombs, a spokesman for the British government's Near Earth Object Information Centre told BBC radio.
The Centre issued the warning about the asteroid after the giant rock was first observed in New Mexico, United States, by the Lincoln Near Earth Asteroid Research Programme.
"The Near Earth Object will be observable from Earth for the next two months and astronomers will continue to track it over this period," said Dr Alan Fitzsimmons, one member of the expert team advising the Centre.
"On impact, it could have the effect of 20 million Hiroshima atomic bombs"
Spokesman, Near Earth Object Information Centre
Asteroids such as 2003 QQ47 are chunks of rock left over from the formation of the solar system 4.5 billion years ago. Most are kept at a safe distance from the Earth in the asteroid belt, between Mars and Jupiter.
But the gravitational influence of giant planets such as Jupiter can nudge asteroids out of these safe orbits and send them plunging towards the Earth.