** Shares of U.S. rare earth miners rise after President Donald Trump said he is weighing a "massive increase" in tariffs on Chinese imports

** Trump's comments come a day after China said it would tighten export controls on rare earth minerals

** China produces over 90% of the world's processed rare earths and rare earth magnets; U.S. has only one rare earth mine

** Analysts expect U.S. to ramp up efforts towards reducing reliance on China, with increased investments and government support for developing a mine-to-magnet supply chain, along with more agreements and collaborations

** Shares of Critical Metals CRML.O surge over 18% to $17.36

** USA Rare Earth USAR.O jumps 12.4%, MP Materials MP.N rises ~10%, NioCorp NB.O up ~9% and Energy Fuels rises 8%

** Ramaco Resources METC.O up 3% and Trilogy Metals TMQ.TO rises 1.6%

(Reporting by Vallari Srivastava in Bengaluru)

((Srivastava.Vallari@thomsonreuters.com;))