An attempt by scientists to raise the orbit of the International Space Station (ISS) failed early Thursday, Russian space officials said.

　　"The lid on the correcting engine KD-2 did not fully open during the maneuver, so we decided to cancel the operation," an official in the mission control center near Moscow said as quoted by the ITAR-TASS news agency.

　　Experts were trying to establish what went wrong before attempting to re-start the operation on Friday, the official said.

　　The ISS crew, US astronaut Jeffrey Williams and Russian cosmonaut Pavel Vinogradov, "were not asleep when that happened, and it was they who noted the failure as the maneuver was being prepared for," the official added.