Russia is set to pospone the next two manned launches for the International Space Station (ISS) for several weeks due to technical problems with the Soyuz spaceship, an industry source told Interfax Friday.

The source told Interfax that the Soyuz TMA-04M vessel had not withstood tests to its pressure chamber ahead of the planned mission on March 30 and the first flight would be postponed to mid-April or the first half of May.

"This re-entry capsule now cannot be used for manned spaceflight," the source said.

That mission would fly with the re-entry capsule that was due to go up on the next mission on May 30 and as a result that mission would also likely be postponed to the middle or end of June.

The re-entry capsule goes inside the spacecraft and is the portion that eventually returns the astronauts to Earth when the mission is over.

Russia now has sole reponsibility for taking US and other international astronauts to the ISS following the withdrawal of the US space shuttle but its own space programme has been hit by a string of problems in the last months.