The space rock will reach within 11,000 miles of the surface and give off a light bright enough to be seen through a small telescope, experts said today.
It was only spotted on Wednesday by a robotic telescope in New Mexico that scans the skies for such hazards. An alert was then put out yesterday by the International Astronomical Union's Minor Planet Center in Massachusetts.
The find was confirmed by Peter Birtwhistle, who has discovered dozens of asteroids from his own UK observatory, with a photo taken from Great Shefford in Berkshire.
It will be daylight in the UK when the asteroid, which has been named 2011 MD, makes its close encounter over the southern hemisphere.
But astronomers in other parts of the world, such as South America, will be able to watch it brighten and fade rapidly as it speeds through the starry background.
Asteroid 2011 MD is estimated to be between 10 and 50 yards wide.
UK asteroid expert, Dr Emily Baldwin, said: "We are certain that it will miss us, but if it did enter the atmosphere, an asteroid this size would mostly burn up in a brilliant fireball, possibly scattering a few meteorites."
On November 8, a 400-metre wide asteroid weighing 50 million tons, called 2005 YU55, is expected to fly inside the orbit of the moon.