SpaceX is sending its unmanned Dragon cargo ship on its sixth official supply mission to the International Space Station on Monday, should the weather behave itself.
The US space transport company will also seek to recycle the first stage of the Falcon 9 rocket by landing it on an ocean platform soon after launch, set to take place from the Kennedy Space Center in Florida at 4:33 pm (2033 GMT).
The latest weather forecast is for a 60 percent chance of favorable conditions at liftoff time. If it does not launch Monday, the next chance will be Tuesday at 2010 GMT.
After the launch, SpaceX will make another attempt to guide the first stage of its Falcon 9 rocket back to a controlled landing on an ocean platform, part of the California-based company's goal of making rockets one day as reusable as planes.
In January, the rocket attempted a controlled maneuver to land on a barge in the Atlantic, but collided with it instead and broke into pieces.
Since NASA retired its Space Shuttle, Russia's Soyuz is the only spacecraft that can ferry astronauts to and from the orbiting International Space Station. Private company Space X's Dragon is the only re-entry cargo craft.
Boeing and SpaceX are developing reusable astronaut carriers for NASA, which is also working on the Orion craft it hopes will take humans to Mars.
If all goes well, Dragon will make it to the ISS Wednesday. It should be guided into the station by European Space Agency astronaut Samantha Cristoforetti.
SpaceX officials are feeling upbeat because of some technical improvements to help in the event of strong winds, and the positive weather outlook.
"I guess together the improvements of the vehicle, the first stage of Falcon 9 and the improvements of the drone ship, I will up my probabilities (of success) to 75 percent, maybe 80 percent at this point in time," Hans Koenigsmann, vice president and chief engineer at SpaceX, told reporters.
The ISS crew can't step out for groceries so Dragon is bringing a two-tonne order of food and water from NASA, and even an espresso machine. There are also materials for future research on the effects of weightlessness.
After a five-week stay docked with the ISS, Dragon will leave the station and head home to Earth loaded with no longer needed scientific equipment, garbage and other items.
This marks SpaceX's sixth ISS supply mission for NASA out of a total of 12, under a $1.6 billion contract.