A pair of US astronauts successfully replaced a failed backup computer on the International Space Station (ISS) on Wednesday during a short spacewalk, US space agency NASA said.

Astronauts Steve Swanson and Rick Mastracchio began their spacewalk at 9:56 a.m. EDT (1356 GMT) to replace a Multiplexer/ Demultiplexer (MDM) back up computer, which failed to respond to commands on April 11 during a routine health check.

The task was originally scheduled for two and a half hours but it took the duo only one and 36 minutes to get the job done.

"Swanson and Mastracchio installed a spare MDM that was housed inside the Destiny lab since April 2001 when it was delivered aboard space shuttle Endeavour," NASA said in a statement.

"They removed the failed MDM from the S0 truss where it has been located since the truss was delivered with the MDM already inside in April 2002," it said.

The ISS houses 45 MDMs, 24 internally and 21 externally, and the failed one provides commands to truss systems, solar alpha rotary joints and the Mobile Transporter rail car which rides along the truss structure, the agency said.

A few hours before the spacewalk, a Russian resupply ship Progress 53 undocked from the ISS, NASA said.

"It will back up about 311 miles (about 500 kilometer) from the space station so Russian mission controllers can test its upgraded Kurs automated rendezvous system," it said.

The unmanned spacecraft is expected to redock again at 8:15 a.m. EDT (1215 GMT) Friday to the Zvezda service module after the Kurs tests are complete, the space agency added.

The last time a Progress cargo freighter pulled away from the station and redocked was in July 2012. The Progress 47 space freighter undocked from the Pirs docking compartment for an eight- day test of the Kurs automated rendezvous system before redocking to the same port.