American space agency NASA said in a recent statement that astronauts aboard the International space station (ISS) will be attempting an unplanned spacewalk to fix a railcar which is used by station’s robotic arm.

As per agency officials, NASA astronauts Scott Kelly and Tim Kopra will be going for the spacewalk outside the station to free the outpost’s Mobile transporter railcar, which suddenly stopped moving on Wednesday.

The surprise spacewalk might occur as early as Monday, said NASA. The problem of the railcar will be fixed before the arrival of unmanned Russian Progress cargo ship on December 23, it added.

NASA engineers said the railcar might have been stalled due to a stuck brake handle, said Kenny Todd, the station's Mission Integration and Operations Manager at NASA's Mission Control center in Houston.

As per experts, the ISS’s Mobile Transporter is a rail-based platform that allows the space station’s robotic arm to reach most of the orbiting lab.

Presently the railcar is around 4 inches (10 centimeters) from its intended latch point and is near the center of the station’s main truss, said NASA experts.

Todd recently in an interview on NASA TV said that engineers will evaluate the stuck railcar and swill soon come up with a plan to free it most probably within a week’s time.

He said that the space station management team will be meeting on Sunday, December 20 to decide whether to go ahead with the spacewalk on Monday or delay it until Tuesday.