China exercises a virtual monopoly on so-called "rare earth" metals, essential for everything from household appliances to cars, energy and weapons.

"All the rare earths has been settled, and that's for the world," Trump told reporters aboard Air Force One, adding that the deal was for a year and would be re-negotiated annually.

During his Asia tour, Trump also signed a deal with Japan securing supplies of critical minerals and rare earths.

"There's no roadblock at all on rare earths -- that will hopefully disappear from our vocabulary for a little while," he said.