Argentina tonight accused the UK of deploying nuclear weapons near the Falklands.
Foreign minister Hector Timerman made the claim as he urged the United Nations to intervene in the long-running dispute over the islands.
He said Buenos Aires had intelligence that a Vanguard submarine had been deployed in the area.
"Thus far the UK refuses to say whether it is true or not," Mr Timerman told a press conference in New York through a translator. "Are there nuclear weapons or are there not?
"The information Argentina has is that there are these nuclear weapons."
Mr Timerman accused Britain of using an "unjustified defence of self-determination" to maintain a military base on the Falklands, which allowed her to dominate the Atlantic.
"It is perhaps the last refuge of a declining empire," he insisted. "It is perhaps the last ocean that is controlled by the UK."
He said Britain had been "colonialist throughout (her) history", and should now "give peace a chance".
At a separate press conference immediately afterwards, Britain's ambassador to the UN, Sir Mark Lyall Grant said the Government did "not comment on the disposition of nuclear weapons, submarines etc".
But he branded the idea that the UK was "militarising" the situation "manifestly absurd".
"Before 1982 there was a minimal defence presence in the Falkland Islands," he said.
"It is only because Argentina illegally invaded the Falkland Islands in 1982 that since then we had to increase our defence posture.
"Nothing has changed in that defence posture in recent months or recent years."
Sir Mark said the UK had been in the Falklands since before Argentina existed, and the islanders were entitled to self-determination under the UN charter.
Tensions between the two nations have been growing over recent months, with David Cameron and Argentine president Cristina Kirchner trading barbs.
The UK has insisted that the deployment of one of its most modern destroyers, HMS Dauntless, to the region is merely routine.
The Duke of Cambridge's arrival in the Falklands for a posting as as an RAF search and rescue pilot has further infuriated Buenos Aires.
And there were protests after the website of local Falklands newspaper the Penguin News ran a photo of Mrs Kirchner labelled "bitch", in an apparent accidental slip.
Earlier, UN Secretary General Ban Ki-moon issued a statement expressing "concern about the increasingly strong exchanges" between the two governments.
After holding talks with Mr Timerman, he said the international body would be happy to help mediate the dispute if asked.