(Reuters) - A SpaceX Crew Dragon space capsule, which is due to bring home stuck astronauts Butch Wilmore and Suni Williams next year, arrived at the International Space Station (ISS) on Sunday, according to NASA and SpaceX.

NASA astronaut Nick Hague and Roscosmos cosmonaut Aleksandr Gorbunov boarded the ISS shortly after the Dragon capsule docked at the station at 2130 GMT, NASA said in a post on X.

The SpaceX Crew-9 mission was supposed to transport four astronauts to the ISS until two empty seats had to be opened up for Wilmore and Williams after the Boeing Starliner capsule they arrived on in June was deemed unfit to return them to Earth.

The two former military test pilots have been stuck on the ISS since then after the Starliner capsule suffered thruster failures and helium leaks. NASA decided it wasn't safe for the astronauts to return on Starliner, which was sent back to Earth empty earlier this month.

Wilmore and Williams, who were the first crew to fly on the troubled Starliner, are now due to return home with Hague and Gorbunov on Crew Dragon in February next year, as what was supposed to be an 8-day mission has turned into an 8-month ordeal.

(Reporting by Joe Brock; Editing by Lincoln Feast.)