Baikonur, Kazakhstan - Space powers Russia and the United States are set to fly together on Wednesday to the International Space Station (ISS), the first joint mission since Moscow invaded Ukraine.

On board the Soyuz capsule will be cosmonauts Sergei Prokopyev and Dmitry Petelin, as well as NASA astronaut Frank Rubio. They are scheduled to blast off at 6:54 PM from Russia's Baikonur Cosmodrome in the steppes of Kazakhstan in Central Asia.

The flight to the orbiting human outpost will last three hours. The trio are due to spend six months there.

Speaking a few weeks ago, Rubio called it "an incredibly important mission" and said he had become "good friends" with his Russian crew-mates.

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Rubio called the cooperation between NASA and Russian space agency Roscosmos "good and strong," despite the heightened tensions between Moscow and Washington.

Russia complains that sanctions imposed by the US and EU are hampering its space-related work, including production of rockets, which also have military applications.

"I think it's important when we're at moments of possible tension elsewhere that human space flight and exploration – something both agencies are passionate about – that that remains a form of diplomacy and partnership where we can find common ground and keep achieving great things together," Rubio said.

Russia recently said it would withdraw from the aging space station after 2024 in light of its conflict with the West over Ukraine. No exact date was given and some analysts doubt Russia will follow through.

Cosmonaut Prokopyev said recently that 48 experiments are planned during the 68th space station mission, including work with a 3D printer in zero gravity.

While it is the second flight into space for Prokopyev, Petelin and Rubio are flying for the first time. The three will have company on the ISS, some 250 miles above the Earth.

Already on board are the commander of the 67th expedition, Oleg Artemyev, along with fellow cosmonauts Dennis Matveev and Sergei Korsakov. NASA astronauts Bob Hines, Kjell Lindgren, and Jessica Watkins are there, as well as the Italian Samantha Cristoforetti from the European Space Agency.