The diplomatic row over the Falkland Islands deepened dramatically after Argentina announced that it would take its protests over British oil exploration to the United Nations today.

At the Rio Group summit in Mexico yesterday, Buenos Aires won unprecedented support from other Latin American states for its demand that the UK stop drilling in waters near the islands.

Argentina’s Foreign Minister is to meet the UN Secretary-General, Ban Ki Moon. A resolution is also set to be tabled in the UN General Assembly condemning Britain for allowing Ocean Guardian to begin drilling 60 miles north of the islands after Argentina annouced new shipping controls. Desire Petroleum, which is operating the rig, has said that the drilling will take about a month. Further exploration is likely by other companies.

David Miliband, the Foreign Secretary, insisted that the exploration was fully within international law. But ministers admit privately that the UK has been preparing for a diplomatic confrontation with Argentina for months.

Although both sides played down the prospect of renewed military conflict, a government source told The Times that a submarine had been made available to supplement the routine military presence, although it is not yet in waters off the Falklands. The Ministry of Defence said that HMS York, a frigate, was expected to remain there for the foreseeable future. The Falklands air defences were quietly upgraded late last year with the arrival of four Typhoon jets.

At the Rio Group summit, Argentina scored a coup in the war of words when 32 heads of state backed its “legitimate rights . . . in the sovereignty dispute with Great Britain”. Hugo Chávez, the Venezuelan President, used a television address to reiterate his support, bellowing: “Give the Falkland Islands back to Argentina, Queen of England.” But it was the backing of countries such as Chile and Brazil that has concerned British diplomats.

Cristina Fernández de Kirchner, Argentina’s President, said that Britain had broken a UN resolution forbidding unilateral development in disputed waters. She accused Britain of double standards in its pursuit of the islands’ natural resources but ruled out any military engagement or attempt to block shipping.

British officials said that Gordon Brown and Mr Miliband would wait for the outcome of events at the UN before deciding how to respond. Diplomats in Latin America believe that President Kirchner is using the issue for domestic purposes. “This is principally a PR campaign, not a serious legal or diplomatic effort,” said one.

The US offered Britain only tepid support. The State Department said that it took no position on the sovereignty claims of either country.

White House officials contacted by The Times would not be quoted on the dispute — not for fear of being drawn into a diplomatic showdown but because, as one admitted, it had barely registered as a concern for the Administration. A generation ago President Reagan was slow to back publicly Britain’s efforts to recapture the islands, but US intelligence proved critical to British military success.

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