Argentina's foreign minister has accused Britain of sending a nuclear-armed submarine to the South Atlantic.
The two countries went to war in 1982 over the Falkland Islands, a British territory whose ownership is disputed by Argentina.
The BBC reports that Argentina's foreign minister, Hector Timerman, has demanded that the UK confirm the location of its nuclear submarines.
He told a news conference at the United Nations in New York that Britain is "militarising the region", repeating earlier accusations made by the President Cristina Fernandez de Kirchner.
But British officials have dismissed the accusations as "absurd".
UN chief Ban Ki-moon earlier called on both sides to avoid escalating tensions over the islands.