U.S. Astronauts Scott Kelly and Timothy Kopra will perform an unplanned spacewalk in the near future in order to repair the mobile transporter on the International Space Station's (ISS) surface, a source with the Russian space industry told Interfax-AVN on Friday.

"The emergency has been prompted by a defect with the Canadian robotic arm's mobile transporter, which got stuck while moving along the main truss of the U.S. segment from one operational point to another," he said.

"The spacewalk has been planned preliminarily for December 21-22 and should not hamper the Progress MS cargo spacecraft's docking slated for December 23," the source said.

Expedition 46/47 crewmembers Yury Malenchenko (Roscosmos), Timothy Kopra (NASA), and Timothy Peake (ESA) arrived at the ISS on December 15.

The crew are supposed to work with the new cargo spacecraft Progress MS. They will also have to receive the U.S. cargo spacecraft Dragon and Cygnus and re-equip the Russian and U.S. segments of the ISS.

The Russian space program on the ISS includes 46 experiments, including five in outer space.