Two Russians and an American joined three colleagues aboard the International Space Station Thursday for a mission that should include receiving the orbiter's first visit from a private spacecraft.

The Soyuz TMA-04M capsule with Russians Gennady Padalka and Sergei Revin and Joseph Acaba of NASA aboard automatically docked with the space station at 0436 GMT.

Russian mission control said the team unsealed the heavy hatch about two hours later and stepped onto to the international orbiter for what is expected to be a 126-day stay.

The trio blasted off from the Baikonur cosmodrome in Kazakhstan on Tuesday morning in Russia's first manned space launch for almost five months after their start date was put back due to technical problems.

The three newcomers join Russian cosmonaut Oleg Kononenko, NASA astronaut Don Pettit and Dutch spaceman Andre Kuipers, who have already been on the station almost five months since their December launch.

Regular space missions stretch as long as six months but the new crew's visit was shortened by initial concerns about the safety of the Soyuz capsule's seal, forcing the replacement of the vessel.

The crew will compensate with a packed schedule comprised of hundreds of experiments and the expected arrival of the first private cargo vessel at the ISS.

Private firm SpaceX is seeking to launch its Dragon spacecraft carrying cargo for the ISS on May 19 from Cape Canaveral, Florida in what the company hopes will be the first step towards an eventual private manned mission.