President Volodymyr Zelenskiy has told Reuters he is ready to do a deal with U.S. President Donald Trump that includes U.S. involvement in developing Ukraine's huge deposits of rare earths and other critical minerals.

With obscure names like lutetium and dysprosium, rare earths are used in everything from iPhones and magnetic resonance imaging machines to missile guidance systems. More recently, demand has been propelled by the green tech that is helping to cut carbon emissions.

Ukraine's leader has reportedly turned down a proposal over access to the country's deposits, citing a lack of security guarantees.