Argentina’s government is celebrating a decision by a UN commission to expand its maritime territory in the South Atlantic Ocean by 35% to include the disputed Falkland islands and beyond.

The Argentine foreign ministry said its waters had increased by 1.7 million square km (0.66 million square miles) and the decision will be key in its dispute with Britain over the islands. Argentina lost a brief, bloody 1982 war with Britain after Argentinian troops seized the South Atlantic archipelago that Latin Americans call the Malvinas.

The UN commission on the limits of the continental shelf sided with Argentina, ratifying the country’s 2009 report fixing the limit of its territory at 200 to 350 miles from its coast.

“This is a historic occasion for Argentina because we’ve made a huge leap in the demarcation of the exterior limit of our continental shelf,” foreign minister Susana Malcorra said. “This reaffirms our sovereignty rights over the resources of our continental shelf.”

Hoy presentamos el límite exterior de la Plataforma Continental Argentina, que reafirma nuestra soberanía en el Atlántico Sur. — Susana Malcorra (@SusanaMalcorra) March 28, 2016

Oil exploration is already pumping millions of dollars into the Falkland Islands economy. Many islanders remain concerned about Argentina’s claim as well as the potential for problems from rapid change brought by the new industry.

The UN commission’s finding included the caveat that there is an unresolved diplomatic dispute between Argentina and Britain over the islands.

The Falklands are internally self-governing, but Britain is responsible for its defence and foreign affairs. The British government says islanders cannot be forced to accept Argentinian sovereignty against their will.

The Falkland Islands government said on Monday it was seeking clarification from the British government on “what, if any, decisions have been made, and what implications there may be” for the territory in relation to the UN ruling.

Cristina Fernández de Kirchner, then Argentina’s president, throws flowers in the Beagle Channel, in Ushuaia, Argentina, during 2012’s commemoration of the 30th anniversary of the Falklands war. Photograph: Leo la Valle/EPA

“As soon as we have any firm information we will make it available,” Mike Summers, chairman of the legislative assembly of the Falkland Islands, said in an emailed statement. “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.”

There was no immediate comment from the British government.