The US space shuttle Endeavour is set to launch on the final orbiter mission of 2008, carrying cargo bound for the International Space Station (ISS).
Endeavour will take equipment to refit the ISS for six crew members, instead of the current three, and will also drop off astronaut Sandra Magnus, BBC reported.
Four spacewalks on the 15-day flight are planned, including repairs to joint damage on the station's solar arrays.
The shuttle will launch from the Kennedy Space Center in Florida.
The orbiter is expected to get away from the launch pad at 0055 GMT on Saturday.
Meteorologists predict a 70% chance the weather will be suitable for Nasa's 124th shuttle launch.
A Nasa spokesman said: "The launch team at Nasa's Kennedy Space Center has started filling the external tank with liquid oxygen and liquid hydrogen.
"The propellants will power Endeavour's three main engines during launch.
"There are no technical issues in work and lift-off remains on schedule."
The mission, STS-126, has been titled "Extreme Home Improvements".
During the 15 days, the crew will conduct four spacewalks, to work on the space station's solar power system.
Working in teams of two, astronauts will emerge from the space station's Quest airlock and work on the two large rotary joints, which turn the station's massive solar array "wings" towards the Sun.
They are to service the starboard side joint and perform preventative maintenance on the port side joint.