The Russian cargo ship that undocked from the International Space Station to perform tests managed to re-couple Sunday after a failed attempt earlier in the week, Russia's space agency said.

"Approach operations and docking took place by automatic pilot," the Russian Space Agency said on its website.

The cargo ship, known as Progress M-15M, had undocked from the station a week earlier to perform tests to facilitate future dockings of cargo ships.

But its recoupling had been postponed Tuesday due to an apparent failure in the new Kurs-NA rendezvous system, according to US space agency NASA.

A Soyuz rocket launched the cargo ship in April from the Baikonur cosmodrome in Kazakhstan with 3.25 tonnes of fuel, food and water aboard to restock the ISS.

There are currently six people on the space station, which orbits 350 kilometres (about 220 miles) above the Earth and is permanently occupied by an international crew.

Russia is now the only nation capable of sending astronauts to the station after the US space shuttle program formally ended last year.

But Russia's space programme has been beset by a litany of technical problems which have resulted in the loss of half a dozen satellites and vehicles over the past year, including an ISS-bound Progress cargo vessel.