Russian President Vladimir Putin has highlighted Russia's cooperation with the United States in space, despite all of the difficulties the two countries face on Earth.

Putin spoke by video link with astronauts from both countries aboard the International Space Station on Tuesday, the day Russia celebrates Cosmonauts Day.

It was on April 12, 1961, that Yuri Gagarin orbited the Earth to become the first man in space.

Putin told the astronauts: "We attach great importance that despite whatever difficulties we face on Earth, people in space work shoulder to shoulder, hand in hand, help each other and fulfill tasks that are essential not just for our countries but for all of humanity."

Putin also spoke by video link with the Vostochny Cosmodrome, under construction in Russia's Far East.