Image caption Mr Kopra was due to be the lead spacewalker on the shuttle's next flight

A US astronaut has lost his place on the next space shuttle mission next month, after falling off his bicycle.

Tim Kopra was injured in a cycling accident at the weekend.

His place as the lead spacewalker on the shuttle's flight will be taken by another astronaut, Steve Bowen.

The mission has been postponed several times because of technical problems. But the last-minute change is not expected to delay Discovery's 24 February launch any further.

Discovery is due to make a cargo-delivery run to the International Space Station.

Nasa has not released details of Mr Kopra's injury, citing medical privacy.

The accident took place near his home and did not involve any other vehicles.

Discovery's launch has been on hold since the autumn to repair cracks in its fuel tank.

The flight is among the final missions for the space shuttles, which are being retired this year.