A Russian spacecraft carrying three astronauts is on track to arrive at the International Space Station after a delay.

Docking with the orbiting outpost was set for Thursday evening.

The trio blasted off from Kazakhstan on Wednesday on what was supposed to be a six-hour "fast track" to the space station. But an engine burn intended to adjust the Soyuz spacecraft's path never occurred, delaying the docking. The American and two Russians on board were not in danger.

Since the space shuttle's retirement, NASA has relied on the Russians to ferry astronauts. It's paying two private companies including SpaceX to transport cargo and eventually astronauts.

NASA says SpaceX's fourth supply run to the set for Sunday has been postponed because of a problem at the launch site.