Asteroid 2016 XK18 will pass Earth on December 18.
The asteroid called 2016 XK18 was discovered this month, and is anything from 42 to 93 metres long, meaning it could destroy a city the size of London if it struck.
But cosmically speaking, that is a cat's whisker, and the US space agency admits it is not year clear of its orbital path.
Each so-called "near-Earth asteroid" is given a condition code from 0 to 9 on how certain it is of its path.
Zero means NASA is certain, whereas nine is highly uncertain.
The new asteroid has been given the second worst code of eight.
NASA classes any object passing within a distance of 30 million miles of Earth as a "near earth object", because orbits are estimated and it is not always certain about the path they will take.
News of the latest close shave comes after a NASA scientist sent out a startling asteroid warning, yesterday, stating that Earth is doomed if there is a collision as we are massively unprepared.
While the chances of an asteroid impact are small, experts believe that one could come crashing towards us at any point.
The last catastrophic asteroid event was 65 million years ago, resulting in the extinction of the last dominant species of the planet, the dinosaurs, and some experts say we will be able to do about as much as they did to prevent it – nothing.
NASA has admitted we are not yet prepared for an asteroid strike.
The biggest problem, basically, is there’s not a hell of a lot we can do about it at the moment.
Speaking at the annual meeting of American Geophysical Union, Dr Joseph Nuth, a researcher with Nasa’s Goddard Space Flight Center, of a potential asteroid collision: "The biggest problem, basically, is there’s not a hell of a lot we can do about it at the moment."
Nasa has made great strides in discovering near-Earth objects that are over one kilometre in size, with 90 per cent now accounted for.
However, that means that there are still 10 per cent of dangerous asteroids that have not been spotted and which could come as a surprise.
But even if scientists did spot them early enough, they would not have sufficient time to prepare to launch a rocket that could knock it of its collision path with Earth.
There are untested plans to use a spacecraft to knock a dangerous asteroid of course, but we would need to know it was coming.
Dr Nuth said: “If you look at the schedule for high-reliability spacecraft and launching them, it takes five years to launch a spacecraft. We had 22 months of total warning.”
Other notable pass being monitored by NASA this month include the monsters 2006 BZ7 and 2102 Tantalus.
The former is estimated at being up to 1.2 miles long - enough to destroy a continent or worse if it hit - but it is expected to pass at a safe 17.8million miles on December 22.
Meanwhile, 2102 Tantalus passes on December 30 at 12.7 million miles.