The International Space Station will be firing up its engines briefly Friday to avoid a piece of debris from the private U.S. satellite Iridium.

The soft-ball sized space debris was on a path that would have brought it about less than a mile close to the station, the NASA said. A collision with a debris can cause a deadly puncture to the space station, thus Mission Control has told astronauts to fire the station's engine to avoid the possibility of the station colliding with it.

The problem of space junk has again caught public attention with the news of the impending re-entry of Russia's Phobos-Grunt spacecraft. Russian officials estimate that the 14.5-ton craft which became stuck in Earth orbit shortly after its Nov. 8 launch, will re-enter the atmosphere in the next few days.

Phobos-Grunt's crash will be the third uncontrolled satellite re-entry in four months, following NASA's defunct UARS craft in September and the dead German ROSAT satellite in October.

According to NASA estimates, Earth's orbital debris cloud contains more than 500,000 pieces larger than a marble and more than 20,000 at least as big as a softball.

While nobody has been known to have been injured by a falling piece of space junk, this problem poses a threat to crafts that orbit and observe the Earth, including those that provide navigation and telecommunication services.

Space junk can also endanger astronauts circling Earth. In June last year, the possibility of a collision between debris and the International Space Station forced the crew of the orbiting lab to take shelter in a docked Soyuz vehicle, in case they needed to make a speedy getaway.

NASA officials has said that Earth's debris cloud is not yet thick enough to seriously affect manned or robotic space operations.

"It's really not too bad right now. We're not losing spacecraft right and left due to debris," said Nick Johnson, chief scientist of NASA's Orbital Debris Program Office at the Johnson Space Center in Houston.

"But later in the century, the situation is going to be noticeably different if we don't do something different," he added.