A unmanned Progress spaceship racing to the ISS with 2.5 tonnes of cargo on board failed Wednesday to deploy a key antenna that helps it dock with the orbiting lab in the latest hitch in Russia's space programme.
"There was a problem with one of the antennae in the Kurs (Navigation) system," Vitaly Lopota of the Energia space corporation the designs Russian spacecraft told the Interfax news agency.
The US space agency NASA said in a tweet: "Once in orbit, an antenna used as a navigational aid on the Progress did not deploy. Russian ground controllers are assessing a fix."
But Lopota stressed that the Progress cargo ship that was launched earlier Wednesday from the Baikonur space station in Kazakhstan could still dock to the International Space Station on Friday as planned.
"Even if the antenna fails to deploy, we will still be able to get to within 200 metres (of the ISS) and perform an automatic docking," the Energia president said.
An unnamed source at Mission Control outside Moscow told news agencies that space officials were not particularly worried about the latest mishap to affect Russia's once-vaunted space programme.
"Such incidents have happened before. Nobody is especially excited about this," said the Mission Control official.
"We will try to get the antenna open when (the Progress) makes its next orbit."
Russia's programme is being watched closely by other space powers because it remains the only nation capable of transporting humans to the International Space Station following the 2011 retirement of the US shuttle programme.
But the Roscosmos space agency has suffered through a string of problems in recent years that include the August 2011 explosion after lift-off of a Soyuz rocket carrying another unmanned Progress cargo craft.