The Kremlin said it expects a Russian imprisoned in the US to be freed under the deal with President Donald Trump that saw American school teacher Marc Fogel released by Russia.

Russia on Sunday declined to confirm or deny a US report of a phone call between US President Donald Trump and Russian President Vladimir Putin, claiming it had not received a good offer to start talks on Ukraine.

Russian President Vladimir Putin and U.S. President Donald Trump have yet to discuss a possible meeting, CNN quoted Kremlin spokesman Dmitry Peskov as saying. It cited Peskov as saying there had been no initial contacts between the two leaders about whether such a meeting was needed or where and how it might take place if it did happen.

Kremlin rejects trading Ukrainian territory for Kursk region, as President Zelenskyy plans a territory exchange to end war.

In an interview with US media, Trump said that one day Ukraine "could become Russia," and did not rule out that he would want to "return" all the money spent by the American government in this country, specifically, an equivalent in the form of Ukrainian rare earth metals worth $500 billion.

Kremlin spokesman Dmitry Peskov has reaffirmed Russia's claim to Ukrainian territories. He said it was a fact that a significant part of Ukraine wanted to become Russia and had already become Russia.