President Trump signed an executive order Thursday that aims to jump-start mining on the ocean floor.

Large-scale deep sea mining has never been done — though some companies have pushed for it — but the seafloor is expected to contain valuable materials. 

A Trump administration official told reporters Thursday that it expects to find manganese, cobalt, nickel and copper at the bottom of the ocean. These materials have energy, weapons and consumer uses, making up components of batteries, steel and more.

The president’s order was expected to direct the Commerce secretary to expedite permits for commercial undersea exploration and mining. It directs the Interior secretary to set a program to allow for mining off U.S. coasts. 

Officials described the measure as a win for both the economy and national security — as China controls a significant share of the world’s mineral supply chains.

Environmental advocates have raised concerns about the potential impacts of deep sea mining, saying it could release toxins, destroy habitats and contribute to biodiversity loss and noise pollution.