The giant space rock, dubbed Asteroid RB4, will reach a nominal distance from the planet just before 6pm UK time today.
NASA’s Pasadena-based Jet Propulsion Laboratory predicts the asteroid will fly by at 5.50pm BTS (4.50pm UT).
If NASA’s calculations are correct, Asteroid RB4 could measure anywhere between 36ft and 82ft (11m and 25m) in diameter.
The size guess would place the formidable asteroid on par with the length of one New Routemaster double-decker bus or two buses in a row.
NASA’s Centre for Near Earth Object Studies has now warned the space rock will make a so-called Near-Earth Object (NEO) Earth Close Approach.
NEOs are all asteroids and comets which threaten to pass the Earth from distance smaller than 1.3 astronomical units (au).
One au is roughly equivalent to the distance between the Earth and the Sun – 92.95 million miles (149.59 million km).
Asteroid RB4 is expected to flyby at a minimal distance of 0.04517au or 4.19 million miles (6.7 million miles).
The distance is just about equivalent to 17.58 times the average distance between the planet and its lunar satellite, the Moon.
Although these incredible distances might seem too big to comprehend from Earth, on a cosmic scale they are absolutely minuscule.
And there is a reason for NASA to pay attention to these asteroids because even the smallest ones have the potential destructive force to wreak havoc on Earth.
Dr Detlef Koschny, a planetary scientist at the European Space Agency, said NEOs can range anywhere from inches to miles in size.
According to the asteroid expert, a space rock of RB4’s size could potentially injure thousands of people if it hit Earth.
He said: “If a 100m asteroid hit Earth, it would cause significant damage in an area the size of Germany, and even affect the surrounding region. But asteroids of this size don’t strike Earth very often. Maybe every 10,000 years on average.
“Going from 100m down to 50m, the statistical frequency of strikes increases to once every 1,000 years.
“Exactly a century ago in 1908, a 40m object struck the Earth over Tunguska, Siberia, destroying an area of forest the size of the Munich metro area.”
Dr Koschny said asteroids up to 65ft (20m) in size like the one which exploded over Chelyabinsk in Russia in 2013, strike once every 10 to 100 years.
The Chelyabinsk asteroid in particular injured more than 1,500 people, knocked out windows across the city and momentarily lit up brighter than the Sun.
Astronomers estimated the asteroid entered Earth’s atmosphere at breakneck speeds between 40,000mph and 42,900mph (19.16 km per second).
Tonight, NASA predicts Asteroid RB4 will barrel through space at a relative speed of 8,052.97 mph (3.6 km per second).