Discovery's crew arrived in Florida on Thursday
The US space agency (Nasa) has started the countdown clock ahead of Monday's launch of the space shuttle Discovery.
The shuttle is due to launch from Florida's Kennedy Space Center at daybreak - around 0621 local time (1121 BST) on a 13-day mission.
Discovery will haul equipment and supplies to the International Space Station (ISS) in a container called a multi-purpose logistics module (MPLM).
The shuttle's seven crew members arrived in Florida on Thursday.
At a news briefing on Friday, Nasa test director Steve Payne said that all launch preparations were proceeding well.
"We're eager to get Discovery flying on Monday morning," he said.
The shuttle weather officer Kathy Winters said there was only a 20% chance of unfavourable weather - in the form of morning fog - on Monday.
The mission is due to include three spacewalks, each lasting around six-and-a-half hours.
Spacewalkers Rick Mastracchio and Clay Anderson will replace one of the space station's gyroscopes, which has failed, and switch an ammonia tank.
Ammonia is used to move excess heat from inside the space station to the radiators outside.
The astronauts will also retrieve a seed experiment that was placed on the exterior of the Japanese laboratory Kibo.
The pressurised MPLM, dubbed a "moving van" by Nasa, will deliver around 7,700kg of cargo to the station, including supplies, a new crew sleeping quarters and science racks which will be transferred to the station's laboratories.
Only four shuttle flights remain - including this one - before the fleet is retired later in 2010.
On Friday, a Soyuz spacecraft carrying Nasa astronaut Tracy Caldwell Dyson and Russian cosmonauts Alexander Skvortsov and Mikhail Kornienko launched from Baikonur Cosmodrome in Kazakhstan.
The three crew members are scheduled to dock with the ISS on Sunday morning (GMT). During their stay, they will carry out experiments and support two shuttle missions to the space station.