MOSCOW (AFP) - Russia's space agency on Saturday (Jan 5) demanded an explanation after Nasa put off a planned visit to the United States by Russia's controversial space chief.
Mr Dmitry Rogozin, a firebrand nationalist politician known for his anti-Western rhetoric, was set to visit the US in February, but Nasa said on Friday that it was postponing his visit indefinitely.
Mr Rogozin, appointed by President Vladimir Putin in May last year and previously a deputy prime minister, is blacklisted and under US sanctions over Russia's actions in Ukraine.
Russia's Roscosmos space agency said in a statement that "it expects official explanations of Nasa's position" and stressed that Mr Rogozin's visit was planned "in accordance with an invitation received earlier".
It added a veiled warning that preparations for talks on cooperation with the US on the International Space Station (ISS) programme and deep space exploration are "so far not suspended".
The row comes as space exploration remains one of the few areas where Washington and Moscow continue active cooperation despite political tensions. The US needs Russia to ferry astronauts to the International Space Station.
Nasa said in a statement on Friday it had told Roscosmos that Mr Rogozin's visit would "need to be postponed" and a new date "has not been identified", USA Today reported.
Plans for Mr Rogozin to visit Nasa's Johnson Space Centre in Houston had prompted protests from US senators.
Democratic Senator Jeanne Shaheen said in a statement on Wednesday that Nasa's invitation to Mr Rogozin "undercuts our message and undermines the United States' core national security objectives".
The rescinded invitation came after Nasa chief Jim Bridenstine visited Russia in October, his first trip after he took up his post.
He observed the failed launch of a Soyuz rocket carrying two Russian and Nasa astronauts, who managed to make an emergency landing.
He told Tass state news agency at the time that Nasa had managed to temporarily lift US sanctions on Mr Rogozin to allow him to visit.
Mr Rogozin has clashed with the US, suggesting American astronauts should use trampolines instead of Russian rockets to reach the ISS after Washington imposed sanctions over Moscow's 2014 annexation of Crimea.
He recently joked Russia would send a mission to the moon to "verify" whether Nasa lunar landings ever took place.