Moscow: A Russian spacecraft carrying a three-man Russian and US crew has docked successfully at the International Space Station after an unprecedented two-day delay caused by a technical hitch.
The Soyuz TMA-12M carrying Russia's Alexander Skvortsov and Oleg Artemyev and NASA's Steve Swanson docked at 3.53am on Friday Moscow time, Russia's mission control said.
"The Soyuz TMA-12M docked automatically to the docking module of the Russian segment of the ISS at 0353 am Moscow time," mission control said in a statement on its website.
The astronauts were expected to open the hatch and cross through into the ISS at 13.40 Australian Eastern Daylight Time on Friday.
The trio were originally to have docked with the ISS early on Wednesday, just six hours after launch from Kazakhstan, but their Soyuz spacecraft suffered a technical glitch on its approach in orbit.
They had to orbit the Earth 34 times before their rendezvous with the international space laboratory, instead of the fast-track route of four orbits originally envisaged.
The issue arose once their Soyuz capsule was in orbit and a thruster failed to fire to assist its approach for docking with the ISS.
US space agency NASA said in a statement on its website that the Soyuz spacecraft "was unable to complete its third thruster burn to fine-tune its approach" to the orbiting space station.
The Soyuz capsule later carried out three manoeuvres in orbit bringing it on the correct trajectory for the adapted two-day route to the ISS.
The head of the Russian rocket state firm Energia that supplies the Soyuz rocket that propels the craft into space however said that the origin of the problem was not yet clear.
"It could be mathematics, it could be a transmitter problem or that the engine choked. But most likely it was a mathematical problem," said Vitaly Lopota on Wednesday, quoted by the Interfax news agency.
This would imply that ground scientists failed to work out the correct altitude in orbit for the thruster to fire to take the Soyuz to the ISS.
A commission has been formed to pinpoint the cause of the error.