WASHINGTON, February 10. /TASS/. NASA is considering the possibility of securing an additional seat for a US astronaut aboard a Russian Soyuz spacecraft to depart to the International Space Station (ISS) this spring, the US space agency said in a statement on Wednesday.

"NASA now is considering obtaining a supplemental seat on the upcoming spring Soyuz crew rotation mission for a NASA astronaut to add additional capability to the agency’s planning," the statement says.

According to the US space agency, it continues to cooperate with Boeing and SpaceX with an aim "to provide safe and reliable crew transportation to and from the International Space Station."

"Securing an additional Soyuz seat assures the back-up capability of at least one U.S. crew member aboard the International Space Station in the event of a problem with either [US] spacecraft," NASA said.

Due to operational constraints, crew members must fly to the station and return on the same spacecraft, NASA said. The crew, which is now aboard the station - Kathleen Rubins and the Crew-1 astronauts - must return on Soyuz and Crew Dragon respectively in April/May.

The launch of the SpaceX spacecraft is scheduled for April 20. However, in case of a launch delay or a premature return, "NASA risks not having a U.S. crew member aboard the International Space Station."

In early November, Russia’s inter-agency commission approved the crew of the 65th long-term expedition that will blast off aboard a Soyuz MS-18 crewed spacecraft from the Baikonur spaceport to the International Space Station in April 2021.

The basic crew includes Oleg Novitsky, Pyotr Dubrov and Sergei Korsakov. The back-up crew consists of Anton Shkaplerov, Andrei Babkin and Dmitry Petelin.

Therefore, a fully Russian crew will set off for the orbital outpost in the spring of 2021. Before that, a fully Russian crew flew to Russia’s Mir orbiter in 2000.