Two astronauts of the International Space Station began their spacewalk Saturday to repair the cooling system whose damaged condition was reported by NASA on Dec. 13.

The spacewalk, transmitted live by the U.S. space agency, began at 1201 GMT.

In the course of their work outside the station, calculated to take more than six hours, the Italian Rick Mastracchio and American Michael Hopkins will have to dismantle the ammonia pump that shut itself down Dec. 11 after sensors detected a temperature anomaly.

Meanwhile, Japan's Koichi Watkata will help lift his colleagues and heavy equipment with a robotic arm, according to a NASA spokesperson in Moscow, cited by local news agencies.

NASA experts do not dismiss the possibility of an ammonia leak when the broken cooling pump is being replaced, something that has occurred previously under similar circumstances.

Should that happen, the astronauts will have to undergo a special cleanup process before reentering the module of the station.

The damage reported by the U.S. space agency has had no serious impact on the operations of the ISS up to now, according to some of the mission's crew.

It did, however, force the Orbital Science company to postpone until mid-January the launch of its capsule Cygnus with supplies for the ISS that had been scheduled for this week.

The next spacewalk to replace the broken cooling pump with the new one is scheduled for Monday, and in case the work is not completed then, another spacewalk will be made on Wednesday.

Besides Mastracchio, Watkata and Hopkins, the ISS Expedition 38's six-person crew is made up of Russians Oleg Kotov, with the rank of commander, Mikail Tyurin and Sergey Ryazanskiy.EFE