The object, named 2023 DZ2, was discovered a month ago.

On Saturday, it will pass within 515,000km of the moon, before flying by Earth hours later.

It is rare for such a huge asteroid - estimated to be between 40 and 90 meters in diameter - to come so close to the planet.

According to Nasa, it's an important opportunity for astronomers to increase their knowledge of asteroids, in the event that a dangerous object were discovered with the potential to hit Earth.

"There is no chance of this 'city killer' striking Earth, but its close approach offers a great opportunity for observations," said the European Space Agency's planetary defense chief, Richard Moissl.

As it is passing just 68,000km away, the asteroid will be visible through binoculars and small telescopes across the globe.

A live web broadcast of its approach will be provided by The Virtual Telescope Project.

The object looks set to return towards Earth's orbit in 2026, but scientists have ruled it out as a threat to the planet on that occasion, too.