The deal comes at a time when prices for uranium, used to fuel most of the world's nuclear reactors supplying 16% of the global energy, have increased significantly last year due to rising demand and limited supply.
E-fuels can offer a solution to power critical segments of transportation such as ships, long-haul aircraft and heavy-duty commercial vehicles, the firm says.
An activist shareholder group said the potential addition of U.S. Steel's 11 blast furnaces to Nippon Steel's operations will almost certainly increase the company's cost of decarbonization.
The southern African nation, one of the top crude producers on the continent, has become a focus for the US in its campaign to secure critical minerals such as copper as it competes against China.