Medvedev is deputy to Russian President Vladimir Putin on the Security Council of Russia, which advises Putin on national security and strategic matters, and is himself a former president and prime minister of the country.

"We're going to send some more weapons – we have to. They have to be able to defend themselves," Trump said of Ukraine July 7.

The US president says he is "not happy" with Russia's Vladimir Putin and that Ukraine is "getting hit very hard".