US President Donald Trump said Chinese leader Xi Jinping has agreed to restart the flow of crucial rare earth materials, after announcing a new round of US-China trade talks will be held in London on Monday.

China views its rare earths as a national security issue, not a trade one, and that’s why Beijing is unlikely to loosen controls anytime soon, experts say.

U.S. President Donald Trump said on Friday that Chinese President Xi Jinping had agreed to restart the flow of rare earth minerals and magnets to the United States. Asked directly by a reporter aboard Air Force One whether Xi had agreed to do so,