The US space agency NASA has decided that Boeing's Starliner will return to Earth without the two astronauts who rode it to the International Space Station.

NASA officials announced the decision at a news conference on Saturday.

The Starliner lifted off with the two crew members onboard for a test flight and reached the ISS in June.

The spacecraft was initially scheduled to bring them back to Earth after about a week, but it has been docked at the ISS for more than two months, after glitches were found in its thruster system.

The two astronauts are now expected to return in February next year on a SpaceX spacecraft, which is scheduled to take off no later than September.

The SpaceX mission will carry only two crew members to the space station, instead of the originally planned four. That is to leave room for the Starliner crew to join them on their return.

NASA Administrator Bill Nelson said the decision is a result of a commitment to safety, and that the agency's core value is safety.

Starliner was originally expected to be a new means to travel between the ISS and Earth, if approved by NASA after the test flight. But the recent change in the plan makes the future uncertain.