Small asteroids pass within this distance of Earth several times each week, but this upcoming approach is "the closest by any known asteroid of this size, or larger, since asteroid Toutatis, a 3.1-mile (five-kilometre) asteroid, which approached within about four lunar distances in September 2004," NASA said.
The next known encounter of an asteroid of comparable size will occur in 2027 when the half-mile-wide (800-meter-wide) asteroid 1999 AN10 will fly by at one lunar distance.
In addition, the encounter on April 19 is also "the closest this asteroid has come to Earth for at least the last 400 years and will be its closest approach for at least the next 500 years," NASA added.
The asteroid will approach Earth from the direction of the sun and will become visible in the night sky after April 19.
It is predicted to brighten to about magnitude 11, when it could be visible in small optical telescopes for one or two nights before it fades as the distance from Earth rapidly increases, NASA added.