The European Space Agency (ESA) has begun preliminary technical discussions with Elon Musk's SpaceX that could lead to the temporary use of its launchers after the Ukraine conflict blocked Western access to Russia's Soyuz rockets.
Aschbacher said talks remained at an exploratory phase and any back-up solution would be temporary.
The political fallout from Russia's invasion of Ukraine has already been a boon for SpaceX's Falcon 9, which has swept up other customers severing ties with Moscow's increasingly isolated space sector.
"But yes, the likelihood of the need for back-up launches is high," he said.
Aschbacher said the Ukraine conflict had demonstrated Europe's decade-long cooperation strategy with Russia in gas supplies and other areas including space was no longer working.
But Borisov later clarified that Russia's plans had not changed and Western officials said Russia's space agency had not communicated any new pullout plans.
"The reality is that operationally, the work on the space station is proceeding, I would say almost nominally," Aschbacher told Reuters
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