President Trump has ordered the U.S. government to take a major step toward mining vast tracts of the ocean floor, a move that is opposed by nearly all other nations, which consider international waters off limits to this kind of industrial activity.

The executive order, signed Thursday, would circumvent a decades-old treaty that every major coastal nation except the United States has ratified. It is the latest example of the Trump administration’s willingness to disregard international institutions and is likely to provoke an outcry from America’s rivals and allies alike.

The order “establishes the U.S. as a global leader in seabed mineral exploration and development both within and beyond national jurisdiction,” according to a text released by the White House.

Mr. Trump’s order instructs the National Oceanic and Atmospheric Administration to expedite permits for companies to mine in both international and U.S. territorial waters.

Parts of the ocean floor are blanketed by potato-size nodules containing valuable minerals like nickel, cobalt and manganese that are essential to advanced technologies that the United States considers critical to its economic and military security, but whose supply chains are increasingly controlled by China.