Argentina’s President, Javier Milei, has threatened international legal action against the UK unless oil exploration at the Sea Lion field near the Falkland Islands is halted within two weeks. The threat sharpens a long-running sovereignty dispute, as the UK-backed project proceeds under licences that the companies say are valid.

Milei said Argentina could pursue arbitration and take the case to the International Tribunal for the Law of the Sea, alleging the project amounts to the illegal exploitation of Argentine resources. Sea Lion lies about 130 miles (209 km) from the islands and is estimated to contain 1.7 billion barrels of oil; British firm Rockhopper Exploration and Israel’s Navitas Petroleum plan to begin extraction within two years. Falkland Islanders voted 99.8% to remain a British overseas territory in a 2013 referendum; the 1982 war resulted in 907 military deaths and three islanders’ deaths.