LONDON, England

A British oil exploration company said Monday it began drilling near the Falkland Islands, a development that could worsen tensions between Britain and Argentina, which fought a war over the disputed islands nearly three decades ago.

Desire Petroleum PLC said it started drilling for oil about 60 miles (100 kilometres) north of the disputed Falkland Islands, despite strong opposition from Argentina. The country claims the south Atlantic islands as its own and calls them Las Malvinas.

“The well is being drilled to an estimated target depth of circa 3,500 metres (11,500 feet),” the company said in a statement. “Drilling operations are expected to take approximately 30 days.”

Argentina lost a seven-week war over the islands to Britain in 1982 and the two countries have since pledged to resolve their differences peacefully. But moves to begin exploiting what could be lucrative reserves of oil and gas around the islands have sent tensions soaring.

The dispute over the Falklands dates back to the 19th century, when the islands were seized by the British. Argentina has sought their return ever since, invading in April 1982 and holding them until June, when British forces retook the territory.

Full diplomatic relations were restored in 1990 and both sides have since largely agreed to disagree on the issue of sovereignty. But anger over the issue still lingers and has been exacerbated by the prospect that Argentina could lose out on mineral wealth discovered offshore.

As the drilling platform made its way to the islands, Argentine President Cristina Fernandez decreed that any ship travelling to or from the islands must get prior permission from her country — a requirement Britain told captains to ignore.

The Latin American nation is taking the diplomatic offensive, lobbying countries at the Rio Group summit of 32 Latin American and Caribbean nations in Playa del Carmen, Mexico.

The summit later backed Argentina’s position. Argentine officials late Monday quoted a statement from Mexican President Felipe Calderon as saying “the heads of state represented here reaffirm their support for the legitimate rights of the republic of Argentina in the sovereignty dispute with Great Britain”.

At the summit, Fernandez condemned what she called Britain’s “unilateral and illegal” exploration in the islands and urged Britain to sit down for sovereignty talks.

Fernandez accused Britain of ignoring international law, but ruled out a military response. She said that “we do not believe in methods like blockades” to keep the British boats or rigs out.

“I thank you all for the support that we have received in this forum for the legitimate rights over Las Malvinas and to appeal to Britain to come to the negotiating table,” she told her fellow leaders.

“Those who have the most power, those who can impose their decisions on others continue using this privilege to ignore international law,” she said. “Argentina will continue working democratically to pursue its claim until we have exhausted all the ways in which we can reaffirm our sovereignty over the southern archipelago.”

Argentine Foreign Minister Jorge Taiana was planning a meeting with UN Secretary-General Ban Ki-moon, seeking help to pressure Britain to follow UN resolutions urging both countries to negotiate their competing claims.

One estimate has put the amount of oil beneath the seabed around the Falklands at 60 billion barrels, something Robert Munks, Americas analyst with IHS Jane’s, said was on par with world-class oil fields.

“Sixty billion barrels is a large amount,” Munks told BBC television. “It’s as large as a large field in Saudi Arabia. But that is only one estimate of several estimates… I should underline of course that there could be nothing there at all. This is all speculative guesswork.”

Venezuelan President Hugo Chavez pledged Sunday to send his armed forces to Argentina’s defence if British attacks, telling his allies they can “have the security of knowing they aren’t alone” against what he called Britain’s threats. But Argentine diplomats have ruled out a military response to what it considers British aggression.

“Get out of there, give the Malvinas back to the Argentine people. Enough already with the empire,” Chavez said.

But Munks said that Argentine anger over the development of the area’s energy wealth was unlikely to translate into military conflict.

“This over-exaggerated talk about war that we’ve seen, that’s not going to come to pass,” he told the broadcaster. “I think it’s going to remain relatively calm.”

Animosity over the issue apparently spilled onto the Internet over the weekend, when the site of Penguin News, the weekly newspaper which serves the Falklands’ approximately 2,500 inhabitants, was hacked.

Office manager Fran Biggs said attackers replaced the site with “a large Argentine flag” and added that the paper had recently received a stream of abusive e-mails from Argentina, with several references to “British pirates”.

But she seemed fairly blase about the rising temperature of the rhetoric surrounding the islands.

“This happens quite a bit,” Biggs said.