Two US astronauts wearing what Nasa assured are ‘healthy’ spacesuits prepared for a spacewalk Saturday to lay cable outside the International Space Station, after an equipment failure briefly delayed the mission.

Commander Barry ‘Butch’ Wilmore and flight engineer Terry Virts were expected to begin at around 1250 GMT the first of several spacewalks aimed at preparing the orbiting outpost for the arrival of US commercial crew capsules, bringing astronauts to low-Earth orbit in the coming years. Initially planned for Friday, the spacewalk was postponed by a day to allow NASA more time to wrap up an investigation into a problem with a piece of equipment inside certain spacesuits. The breakdown in the fan pump separator - which helps control the suit’s temperature - in two of the American spacesuits was part of the same system that failed in 2013 when water flooded the helmet of a spacewalking Italian astronaut, nearly drowning him. In December, when astronauts were doing spacesuit maintenance, they found that the fan pump separator in one suit did not speed up as expected. The same problem with another spacesuit was detected in January. A replacement part that was on board the space station was installed in the suit Virts is wearing, and a new spacesuit was shipped to the space station for Wilmore.

Nasa commentator Rob Navias said early Saturday that both suits are ‘healthy’ and in good working order.