LONDON (Reuters) - Britain said on Friday that Argentinian-led efforts to ban ships flying the Falkland Islands flag from South American ports were "unjustified and counterproductive" and vowed to protect the territory's sovereignty.
The comments by Prime Minister David Cameron were the government's strongest yet as tensions between Britain and Argentina escalated almost 30 years after the two countries went to war over the British-ruled islands.
On Tuesday the South American trading bloc Mercosur announced the ship ban in act of solidarity with Argentina.
"Argentina continues its unjustified and counterproductive efforts to disrupt shipping around the islands and to deter business from engaging in legitimate commerce," Cameron said in a Christmas radio message to the Falkland Islands.
"Let me be absolutely clear. We will always maintain our commitment to you on any question of sovereignty. Your right to self-determination is the cornerstone of our policy," he said.
Britain has controlled the South Atlantic islands, located about 300 miles off the eastern coast Argentina, since 1833. Its two-month war with Argentina in 1982 resulted in the deaths of 255 British and about 650 Argentine soldiers.
The British government says it will only agree to sovereignty talks if the territory's 3,000 residents ask it to, and that the islanders want to remain British.
Argentine President Cristina Fernandez has rejected the argument as a display of "mediocrity bordering on stupidity" and earlier this year called Britain a "crass colonial power in decline" for refusing to hold talks over the islands, known as Las Malvinas in Spanish.
In his radio message, Cameron said it was in British interests to have a constructive relationship with Argentina, but said he would never accept what he said were Argentine efforts to challenge the islands' right to self-determination.
Diplomatic tensions over the islands have increased in recent years over offshore oil exploration.
The spat is also gaining steam ahead of the 30th anniversary of the Falklands war in April, a planned military stint on the islands early next year by RAF helicopter pilot Prince William, and the release of the film "The Iron Lady" about Margaret Thatcher, the former prime minister who led Britain in the war with Argentina.
(Reporting by Mohammed Abbas; Editing by Alessandra Rizzo)