Argentina has been stepping up diplomatic pressure in recent months
Argentine President Cristina Fernandez has urged new UK Prime Minister David Cameron to hold talks over the sovereignty of the Falkland Islands.
The two countries went to war in 1982 after Argentina invaded, with UK forces retaking the territory after a short but bloody conflict.
Mrs Fernandez made her call at the EU-Latin America summit in Madrid.
Foreign Office minister Jeremy Browne said the UK had "no doubt" about its right to sovereignty.
"The principle of self determination as set out in the UN charter applies," he said in a statement.
"There cannot be negotiation on sovereignty unless and until the Falkland Islanders so wish. The Lisbon Treaty clearly reaffirms the EU position that the Falkland Islands is an Overseas Territory of the United Kingdom."
Mr Browne added that the UK and Argentina had a "close and productive relationship" in other areas, including economic issues in the G20, climate change, sustainable development and counter-proliferation.
Mr Cameron was represented at the summit by Foreign Secretary William Hague.
Argentina has long laid claim to the islands in the South Atlantic, which are known in Spanish as Las Malvinas.
In a speech at the summit opening Mrs Fernandez said: "In the name of my country and greeting [the] new prime minister, I would like to request that we please resume our negotiations on sovereignty over the Malvinas Islands."
Argentina has stepped up a diplomatic offensive to try to pressure London into negotiations.
In February, Buenos Aires expressed concern over oil exploration in the islands' waters.
In March, then Prime Minister Gordon Brown rejected talks after Argentina brought up the subject at a G20 summit. It had earlier asked United Nations Secretary General Ban Ki-moon to bring the UK into discussions.
And only last week, the new UK Conservative-Liberal Democrat coalition government rejected a call by Mrs Fernandez to halt the oil exploration being carried out by British companies.
One firm, Rockhopper Exploration, has said that initial data collected from a well "indicated an oil discovery" in the North Falkland Basin.