France on Friday prepared to simulate an attack by a hostile power on one of its satellites in a war game scenario the government said is less outlandishly futuristic than it may seem.

President Emmanuel Macron was to watch onsite as his military chiefs started to play out a four-day sequence in which an unnamed space-capable power attacks a nation allied to France, and tries to take out a French communications satellite.

Germany, Italy and the US are participating in the AsterX space war game at France's national space agency CNES in Toulouse, the first such exercise in France or in Europe.

It is an opportunity to simulate modifying the flight path of satellites, sending backup satellites to fix a breakdown, monitoring the transmission of sensitive data and scrambling transmissions by hostile satellites temporarily or even shutting them down completely.

The scenario of the exercise may be fictional, Macron's office said, but is far from implausible.

The French government accuses Russia of having brought its intelligence-gathering satellite Olymp-K, also known as Louch, into close proximity of the French-Italian military satellite Athena-Fidus in 2017 in what Defence Minister Florence Parly called "an act of espionage".

The largest asteroid to pass by Earth this year will approach within some 1.25 million miles (two million kilometers) of our planet on March 21, NASA said Thursday.

The US space agency said it will allow astronomers to get a rare close look at an asteroid.

The asteroid, 2001 FO32, is estimated to be about 3,000 feet in diameter and was discovered 20 years ago, NASA said.

"We know the orbital path of 2001 FO32 around the Sun very accurately," said Paul Chodas, director of the Center for Near Earth Object Studies. "There is no chance the asteroid will get any closer to Earth than 1.25 million miles."

That is roughly 5.25 times the distance of the Earth from the Moon but still close enough for 2001 FO32 to be classified as a "potentially hazardous asteroid."

NASA said 2001 FO32 will pass by at about 77,000 miles per hour faster than the speed at which most asteroids encounter Earth.

"Currently, little is known about this object, so the very close encounter provides an outstanding opportunity to learn a great deal about this asteroid," said Lance Benner, principal scientist at NASA's Jet Propulsion Laboratory.