Carolyn Cole/Getty ImagesDonald Trump has signed a controversial executive order aimed at stepping up deep-sea mining within US and in international waters.
Thursday's order is the latest issued by the US president to try to increase America's access to minerals used by the aerospace, green technology and healthcare sectors.
The deep sea contains billions of tonnes of potato-shaped rocks, called polymetallic nodules, which are rich in critical minerals like cobalt and rare earths.
Many other countries and environmental groups oppose deep-sea mining in international waters without further research.
The latest US executive order was issued to "establish the United States as a global leader in responsible seabed mineral exploration", it reads.
The move appears to bypass a long-running round of UN negotiations on mining in international waters.
"The US authorisation... violates international law and harms the overall interests of the international community," Chinese foreign ministry spokesman Guo Jiakun said on Friday.
China dominates the production of rare earths and critical metals like cobalt and lithium.
Trump has been frustrated by this relative weakness of the US position, analysts say.
"We want the US to get ahead of China in this resource space under the ocean, on the ocean bottom," a US official said on Thursday.
To achieve this, the order says the US will speed up the process of issuing exploration licences and recovery permits both in its own waters and in "areas beyond national jurisdiction".
The administration estimates that deep-sea mining could boost the country's GDP by $300bn (£225bn) over 10 years and create 100,000 jobs
The EU, the UK and others support a moratorium on the practice until further scientific research is carried out.
Environmentalists and scientists are concerned that undiscovered species living in the deep sea could be harmed by the process.
"Deep-sea mining is a deeply dangerous endeavour for our ocean," said Jeff Watters of Ocean Conservancy, a US-based environmental group.
"The harm caused by deep-sea mining isn't restricted to the ocean floor: it will impact the entire water column, top to bottom, and everyone and everything relying on it," he added in a statement released on Friday.
It is not clear how quickly deep-sea mining could begin but one mining company, The Metals Company (TMC), has already applied for permits in international waters.
TMC's CEO Gerard Barron has previously said he hopes to begin mining by the end of the year.
Along with others in the mining industry, he disputes the environmental claims made and has argued that the abyssal zone - 3,000m to 6,000m below sea level - has very low concentrations of life.
"Here there's zero flora. And if we measure the amount of fauna [animal life], in the form of biomass, there is around 10g per square metre. That compares with more than 30kg of biomass where the world is pushing more nickel extraction, which is our equatorial rainforests," he previously told the BBC.
