Three American astronauts and a Russian cosmonaut are set to launch for the International Space Station on Saturday, the latest crew rotation for the orbital outpost.

A SpaceX Crew Dragon named Endeavour carrying the four is scheduled to blast off atop a Falcon 9 rocket from the Kennedy Space Center in Florida at 11:16 pm (0416 GMT Sunday).

But at midday, SpaceX warned that the chance of favorable weather was only around 40 percent.

Elon Musk's SpaceX has been providing astronaut launch services for NASA since 2020 under NASA's Commercial Crew Program, while a rival program by Boeing has yet to get going.

Matthew Dominick, who leads the "Crew-8" mission, is making his first spaceflight, as is fellow American Jeanette Epps. It will also be the first time for Russian Alexander Grebenkin. Michael Barratt, a physician, is making his third visit to the ISS. His first two were aboard space shuttles, which were discontinued in 2011.

Space remains a rare area of cooperation between the United States and Russia in the wake of Russia's 2022 invasion of Ukraine. The US last month imposed fresh sanctions on 500 Russian targets, seeking also to exact a cost for the death of Russian opposition leader Alexei Navalny in a Siberian prison.

The crew will carry out experiments including using stem cells to create organoids (artificially grown masses of cells resembling organs) to study degenerative diseases, taking advantage of the microgravity environment to enable three-dimensional cell growth not possible on Earth.

Joel Montalbano, NASA's International Space Station program manager, told reporters on a call that the US was keeping a close eye on a "small leak" on the Russian side of the research platform, the latest of several recent issues on the Russian side. A hatch is currently closed to isolate the leak from the rest of the ISS.