Mission managers reviewed images and data gathered overnight and said on Friday they tentatively planned to send American astronauts Chris Cassidy and Tom Marshburn out on Saturday morning to try to stop the leak by replacing a pump on the cooling system.
"The crew is not in danger, and the station continues to operate normally otherwise," Nasa said in a news release.
Ammonia is used to cool the power systems that operate the solar arrays, which provide electricity to the station. Each of the eight solar arrays has its own independent cooling system.
The leak is on the far left side of the station`s truss structure, in an ammonia loop that astronauts previously tried to troubleshoot during a spacewalk in November 2012.
While Cassidy and Marshburn are working outside the space station, crew commander Chris Hadfield, a Canadian astronaut, will choreograph their movements from inside the orbital outpost. Russian cosmonauts Pavel Vinogradov, Alexander Misurkin and Roman Romanenko make up the rest of the crew.
Work was under way to reroute the remaining power channels to maintain full operation of the systems normally controlled by the solar array that is cooled by the leaking loop.
The space station, a $100bn (£65bn) research laboratory that orbits 250 miles (400 km) above Earth, is owned by the United States and Russia in partnership with Europe, Japan and Canada.
More about:
