Dwindling coal exports could be a political headache for Putin, especially amid other bad news for the wartime economy, such as a downturn in manufacturing and warnings by Russian officials about inflation and high interest rates.

US President Donald Trump and Russia's leader Vladimir Putin have spoken for nearly an hour to negotiate solutions on Ukraine.

The chat was the leaders’ second in a month and comes days after the U.S. paused deliveries of some defensive weapons to embattled Ukraine.