A Russian Soyuz spacecraft failed to dock with the International Space Station Saturday.
The craft was carrying a humanoid robot that was scheduled to conduct a mission on the station with the cosmonauts who are there.
NASA said on its blog that the docking system of the Soyuz spacecraft failed to properly lock onto its target on the ISS.
The Soyuz has backed away from the ISS while the cosmonauts work on the station's docking system.
Officials say the Soyuz will attempt another ISS docking Monday.