In a text adopted Monday, the ISA's executive body urged its legal and technical commission to "pay specific attention" to companies whose activities could be in "potential non-compliance" with international law.

The wording was a clear reference to TMC, which turned its back on the ISA and its jurisdiction in filing a US application in April for a deep sea mining permit.

The move came after US President Donald Trump issued an executive order calling for his administration to unilaterally issue mining licenses -- including in international waters.

If approved, it would be the first such license issued by any country or body.

Should the ISA commission find TMC in violation of international law, the company could lose its exploration permits previously issued by the authority.

Nori (Nauru Ocean Resources Inc.), a subsidiary of TMC, has held since 2011 an exploration contract for an area of the Clarion-Clipperton Zone in the Pacific Ocean, which expires in one year.

"It must be clear by now to TMC and its subsidiaries that they face a significant risk of losing their exploration contracts," said Matthew Gianni of the Deep Sea Conservation Coalition, an NGO alliance.

Louisa Casson, who leads Greenpeace's Stop Deep Sea Mining campaign, said the ISA was sending a "stark warning" to others who might consider the same "reckless path" taken by TMC.

Nations are divided over the desire to exploit the ocean depths for nodules -- rich in metals needed for electric vehicles and other emerging technologies -- and worries about disrupting, or possibly decimating, fragile ecosystems.

After more than a decade of negotiations, the ISA has yet to reach agreement on rules to govern the sector.

The United States is not party to the independent ISA or to the UN Convention on the Law of the Sea (UNCLOS), under which the ISA was established in 1994.