Russia's space agency said on Wednesday it had ordered extra checks to be made on its Proton-M rockets, meaning it might be forced to delay some satellite launches this year.
Roscosmos, the Russian equivalent of NASA, made the announcement after the Kommersant daily reported that manufacturing problems had been detected in some Proton-M rockets and that some launches were likely to be delayed by several months "in a best case scenario."
European, U.S. and Asian firms rely heavily on Russia to launch their commercial satellites, and a Roscosmos source told Kommersant that Moscow planned to launch 27 rockets this year, eight of which were Proton-Ms.
"Additional tests (on the Proton-M) are being carried out. That explains the possible delay in launches," said a spokesman for Roscosmos, without providing details. Igor Burenkov, a spokesman for the corporation, said it would become clear after the tests if there would definitely be delays and for how long.
Kommersant reported that the problem was linked to components used in the rockets' engines and concerns that some of them were not sufficiently heat-resistant.
Kremlin spokesman Dmitry Peskov played down the problems, saying Roscosmos did suffer some setbacks, but that it also had great success in many areas.
An unmanned Russian cargo ship loaded with supplies for the International Space Station broke apart about six minutes after lift-off in December. It was carried by a Soyuz rocket.