NASA officials have said the collaboration between U.S. and Russia for space initiatives have yet to be affected by existing political tensions between the two countries, Politico reported Wednesday.

Leigh Munsil writes Meredith McKay, deputy director for human exploration and operations of the international and interagency relations office at NASA, said the space agency’s crew talks frequently with Russian cosmonauts.

“Cooperation internationally with NASA pretty much covers the breadth of what we do, and Russia is one of our biggest partners,” McKay said in the report.

The two nations are expected to collaborate for NASA’s scheduled Space Launch System and Orion spacecraft missions, which aim to explore the moon and asteroids as well as to allow human travel to Mars, the report said.

Russian spacecrafts are currently the only existing transport for U.S. to send missions into space due to the NASA Space Shuttle retirement in 2011, Politico reports.

Al Sofge, director of human exploration and operations division at NASA, said in the report there are still challenges when it comes to collaborating with another nation, such as differences in processes, budget availability and leadership commitment in space matters.