California-based SpaceX on Friday prepared to launch its Dragon cargo carrier to deliver food and supplies to the International Space Station, but a 50-50 weather forecast threatened to postpone the launch.
The journey by SpaceX's unmanned Dragon cargo capsule would be the fifth for SpaceX, and the fourth in a series of SpaceX's contracted supply missions with NASA.
Blastoff is scheduled for 2:16 am Eastern time on Saturday (0616 GMT) from Cape Canaveral, Florida.
If all goes as planned, the supply ship would arrive at the space station at around 7:30 am (1130 GMT) on Monday.
"The weather certainly does look interesting over the next several hours," said NASA weather officer Kathy Winters, saying there was a 50 percent chance that showers or thick clouds could delay the launch.
In case of postponement, another attempt could be made on Sunday or Tuesday, said International Space Station deputy program manager Dan Hartman.
The supply ship is carrying 5,000 pounds (2,300 kilograms) of supplies, food, and equipment for the six-member crew at the orbiting outpost.
"Science payloads include the ISS-Rapid Scatterometer to monitor ocean surface wind speed and direction," NASA said in a statement.
The craft is also carrying a couple dozen live mice in "new biomedical hardware that will help facilitate prolonged biological studies of rodents in microgravity," the space agency said.
A small flowering plant related to cabbage is on board to help scientists study plant growth in space.
SpaceX in 2010 became the first private company to send a spacecraft to the ISS.
The company is run by Internet mogul Elon Musk, who accumulated his fortune by co-founding PayPal and also runs Tesla Motors.
SpaceX this week was awarded a $2 billion contract from NASA to continue developing its Dragon V2 vehicle with the goal of sending people to the space station as early as 2017.
Boeing won a larger NASA contract, more than $4 billion, for the development of its CST-10 crew vehicle.