A roughly 650-metre near-Earth asteroid discovered nearly three years ago will fly safely past Earth on April 19, NASA has said.

The space rock is set to go past Earth at a distance of about 1.8 million km or about 4.6 times the distance from Earth to the moon.

Although there is no possibility for the asteroid to collide with our planet, the upcoming approach will be "very close" for an asteroid of this size.

The asteroid, known as 2014 JO25, was discovered in May 2014 by astronomers at the Catalina Sky Survey near Tucson, Arizona -- a project of NASA's NEO (near-Earth object) Observations Programme in collaboration with the University of Arizona.

The surface of the asteroid is about twice as reflective as that of the moon, according to the scientists.

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.

"Small asteroids pass within this distance of Earth several times each week but this upcoming close approach is the closest by any known asteroid of this size, or larger, since asteroid Toutatis, a five-kilometre asteroid, which approached within about four lunar distances in September 2004," NASA said in a statement on Friday.

The encounter on April 19 is 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.

The next known encounter of an asteroid of comparable size will occur in 2027 when the 800-meter-wide asteroid 1999 AN10 will fly by at one lunar distance, about 380,000 km.

The April 19 encounter provides an outstanding opportunity to study this asteroid and astronomers plan to observe it with telescopes around the world to learn as much about it as possible.

Also on April 19, the comet PanSTARRS (C/2015 ER61) will make its closest approach to Earth, at a very safe distance of 175 million km, NASA said.