US astronomers are warning of a possible Earth-asteroid collision in 2014, UK Government's Near Earth Object Centre said Tuesday. The British agency responsible for identifying potentially hazardous asteroids said US astronomers have discovered a large, fast-approaching asteroid that could hit the earth on March 21, 2014. However, chances of it doing so are said to be just 1 in 909,000. Any risk of an impact is also likely to decrease as further data is gathered, scientists said. The rock is said to measure approximately two thirds of a mile across, which is one tenth of the size of the meteor thought to have wiped out the dinosaurs 65 million years ago.