The European Space Agency says an asteroid believed to pose a remote risk of colliding with Earth this century is bigger than previously thought.
The asteroid, Apophis, will pass by Earth on Wednesday.
Previous estimates by NASA put the asteroid's average diameter at 270 metres.
The European Space Agency said deep space telecospe scans at the weekend showed the asteroid is actually 325 metres.
Named after the god of evil and darkness in Egyptian mythology, Apophis was first detected in 2004.
Early calculations suggested a 2.7% probability of a collision in 2029, but the risk was downgraded after further observations.
Apophis will pass at a safe distance of about 14 million km and will not be visible to the naked eye. However, scientists will be tracking its progress and assessing its future risk.
Space researcher Dr Duncan Steel said it will come much closer in 2029.