The US president says he was more confident of a "peace deal" after Tuesday's talks in Saudi Arabia, in which Russian and American officials also agreed to explore closer relations and economic cooperation.

Russia, like U.S. President Donald Trump, covets Ukraine's natural resources - and on the ground its forces are closing in on a giant lithium deposit. Trump said this month he wants Kyiv to hand over large quantities of its critical minerals in return for U.

Vast estimated deposits of lithium, titanium and rare earths such as scandium have yet to be significantly developed