The United Nations has expanded Argentina's maritime territory to include the waters surrounding the Falkland Islands.
This decision by the UN Commission on the Limits of the Continental Shelf was welcomed by Argentina, and gives the country fresh impetus in its continued claims to the British overseas territory.
It will increase the size of Argentina's territory in the South Atlantic by 35 per cent, but members of the islands' legislative body have expressed concern over the control of natural resources found in the surrounding waters.
Oil exploration has been injecting millions into the economy in the Falklands, which was previously used for farming and strategic military purposes.
Mike Summers, chairman of the Legislative Assembly of the Falkland Islands, said: "Our understanding has always been that the UN would not make any determination on applications for continental shelf extension in areas where there are competing claims."
The UN commission's ruling included a caveat referencing the unresolved diplomatic dispute between Argentina and Britain over the islands.
Argentina's foreign minister Susana Malcorra said the "historic" decision "reaffirms our sovereignty rights over the resources of our continental shelf".
The Falkland Islands are self-governing but Britain is responsible for their defence and foreign affairs coming to their aid during an invasion by Argentina in 1982.
The British government says islanders cannot be forced to accept Argentine sovereignty against their will.
