US astronaut Michael Finke and Russian cosmonaut Gennady Padalk were due to spend around six hours installing the new equipment on the outside of the station which will allow the cargo vessel to dock automatically, Valery Lyndin, spokesman for the space flight control centre in Moscow told Interfax.

The Automated Transfer Vehicle (ATV), a 20-tonne unmanned vessel, will bring fuel, oxygen, water and provisions for the crew. The vessel will also correct the station's orbit and compensate for its regular losses of altitude, the control centre said earlier.

The ATV will be launched into orbit from an Ariane-5 rocket which will blast off from Kourou in French Guiana "in October 2005" the European Space Agency's (ESA) representative in Russia, Alain Fournier-Sicre, told AFP.

Since the Columbia shuttle disaster in February 2003, Russia's Progress cargo ships have been the only way to send supplies to the ISS.

Tuesday's spacewalk is the third to be undertaken by the current crew who have been in orbit since April.

SPACE.WIRE