France says it has extended the continental shelf off several of its overseas territories, including New Caledonia, by a total of half a million square kilometres.
This follows a favourable recommendation by the United Nations' Commission on the Limits of the Continental Shelf.
The move, which also applies to Guyana, Guadeloupe and Martinique, allows France to claim control over the sea shelf beyond the internationally recognised 200-mile Exclusive Economic Zone.
France, which has islands in the Atlantic, Pacific and Indian Ocean, has the world's second largest maritime zone.
Two years ago, the French Economic, Social and Environmental Council urged the government to secure resources in the seabed off France's overseas territories.
In a report, the Council said the Law of the Sea allows for France to lay claim to an additional two million square kilometres, half of which are in French Polynesia.
It says France would be negligent not to profit from this as French Polynesia has rare earths, whose reserves are held by China in a near monopoly.
