The head of Russia's space agency and a former U.S. astronaut have been arguing on social media

A very public dispute has been taking place between the head of Russia’s space agency and a former American astronaut.

Dmitry Rogozin, the director general of Roscosmos, has repeatedly in recent weeks tweeted his support for Russia's invasion of Ukraine and threatened to stop cooperating on the International Space Station.

On March 2, Rogozin shared a video of technicians at the Baikonur Cosmodome taping over the Japanese and American flags fixed onto the exterior of a Soyuz rocket.

"The launchers at Baikonur decided that without the flags of some countries, our rocket would look more beautiful," Rogozin said in a Russian-language tweet.

Former American astronaut Scott Kelly, who has in recent weeks tweeted his support for Ukraine, replied in Russian to the Rogozin’s video post.

"Dimon, without those flags and the foreign exchange they bring in, your space program won't be worth a damn. Maybe you can find a job at McDonald's if McDonald's still exists in Russia."

'Dimon' is a common Russian nickname for people named Dmitry.

On Monday, Kelly shared a screenshot that appeared to show that he had been blocked on Twitter by Rogozin. He also shared another screenshot of a deleted tweet to Kelly by Rogozin translated into English.

"Get off, you moron!" Rogozin's deleted tweet said. "Otherwise the death of the #ISS (International Space Station) will be on your conscience."

Rogozin also took issue with Kelly's familiar use of 'Dimon' in his tweets and called the former astronaut "defiant and destructive."

"Perhaps the dementia and aggression that you have developed is a consequence of the overload and stress of four flights into space. I invite you to undergo an examination at the Brain Institute of our Federal Medical and Biological Agency," Rogozin said in an English tweet.

Kelly previously spent three of four spaceflights on the ISS. According to his website, in October 2015, he set the record for the total accumulated number of days spent in space.

Rogozin also tweeted that other American astronauts of have a "hatred of Russia."

"In a sense, this is even useful: some of our beautiful-hearted colleagues will lose stupid illusions," he said in Russian. "The bet on the creation of national, Russian manned systems is now obvious to everyone."

International collaboration on the ISS is a longstanding tradition and has continued throughout past conflicts with Russia, including the annexation of Crimea in 2014. But recent social media posts from Rogozin and Roscosmos suggest that careful diplomacy in space may be breaking down.

Russia recently delayed the launch of several rockets and announced on March 3 that it will not cooperate with Germany on joint experiments on the Russian segment of the ISS. Roscosmos also said it will be adjusting its space program to prioritize the building of satellites for defence purposes.