Russia and the US are discussing the possibility to continue flights of international crews to the International Space Station (ISS) after the start of the use by Americans of their own spaceships, said head of the Gagarin Research & Test Cosmonaut Training Center Pavel Vlasov in a conversation with reporters.

Russia remains the only country that is currently delivering crews to the ISS.

"There is a discussion currently to enable us fly as mixed crews. That is, NASA astronauts continue to fly aboard Soyuz spacecraft one by one, and our [Russian cosmonauts] will fly aboard NASA spaceships as well," he said.

It will enhance the reliability of ISS missions in case of any launch delays, Vlasov said. After the closure of the Space Shuttle project in 2011, the US lost independent access to space. US astronauts have been flying to the ISS onboard Russian Soyuz aircraft only since then. Boeing and SpaceX are expected to make the first piloted flight before the end of 2018 or in mid-2019, with not strict timeline determined yet.