The undocking of a supply craft from the International Space Station (ISS) will take place Friday after a three-day delay, the European Space Agency (ESA) said.

The robot freighter should have separated from the ISS on Tuesday, the first step towards a suicide plunge over the South Pacific.

But the operation was postponed because the astronauts sent the craft a wrong identification code, which prevented a datalink from being established, it said.

"Departure of ATV-3 from the ISS is now planned for 28 September, around 2015 GMT," ESA said Thursday on its blog for the Automated Transfer Vehicle (ATV).

Named after a 20th-century Italian physicist, the Edoardo Amaldi is the third of five ATVs that ESA is providing as a partner in the ISS project.

The craft, each the size of a London double-decker bus, are designed to make one-way trips to the space station, which currently has three people on board.

They haul up tonnes of food, water, air, equipment and other supplies, navigating their way by the position of the stars and docking automatically.

The ATVs then use onboard engines to provide occasional boosts to the ISS, whose altitude drops because it is in low orbit and dragged by lingering atmospheric molecules.

At the end of their trip, laden with rubbish and human waste, the ATVs detach and several days later burn up in a controlled destruction over the ocean.

After fixing the datalink problem, mission managers scheduled a new departure time for the Edoardo Amaldi for late Thursday, the ESA blog said.

But this was scrapped amid worries that the ISS would have to do an emergency manoeuvre to avoid a dangerous piece of space debris -- a shard of an Indian rocket.

Later analysis showed the debris would comfortably miss the ISS, so the undocking was postponed for a second time, to Friday.