About the size of a minibus, the space rock, known as 2023 BU, will whip over the southern tip of South America.
With a closest expected approach of 3600km, it counts as a close shave.
It illustrates how there are still asteroids of significant size lurking near Earth that remain to be detected.
This one was only picked up last weekend by amateur astronomer Gennadiy Borisov, who operates from Nauchnyi in Crimea, the peninsula Russia seized from Ukraine in 2014.
Follow up observations have refined what we know about 2023 BU's size and, crucially, its orbit.
