A meeting of the UN General Assembly (Photo: AFP/VNA)

The text of the high seas treaty was finally agreed in March, after 15 years of discussions and four years of formal negotiations. The landmark accord would establish a legal framework to extend swaths of environmental protections to international waters around the globe.

But it has yet to be formally adopted, needing first to be scrutinized by legal experts and translated across the UN's six working languages. The meeting to adopt the treaty is "tentatively" set for June 19 and 20.

After its adoption, individual member states then would be able to ratify it.

Currently, almost all protected marine areas lie within individual countries' national territorial waters. The treaty would allow protections to be extended outside of exclusive economic zones (EEZ), which extend to a maximum of 200 nautical miles (370km) from coastlines. More than 60% of the ocean falls outside EEZs.

The treaty would also require environmental impact studies for activities like deep-sea mining.