However, the ultimate concern of Brazilian military strategists is that one day they might end up fighting a foreign power for control of the Amazon.

"The threats today are diverse. (One is) a superior military power to us and we have a strategy to resolve this," said Gen. Claudio Barbosa de Figueiredo, army commander for the Amazon region.

"Another great threat we consider is a power vacuum," he said in an interview at his headquarters on a military base in Manaus, a sweltering port city on the Rio Negro.

Since the end of the 1964-85 military dictatorship, defending the Amazon has become a priority for Brazil's army. In recent years it has built up its troop strength to 22,000 and plans to have 26,000 by the end of 2006, Figueiredo said.

Some 25 special frontier platoons with about 70 men each have been deployed in remote positions, he said.

The area is covered by the Amazon Vigilance System, a network of radars, computers and aircraft that looks for illegal air strips, incursions and environmental damage and which US defense chief Donald Rumsfeld visited last month.

The perceived threat that lurks at the back of many Brazilians' minds is that outsiders covet the Amazon, a fear fanned whenever a foreign politician talks about the forest and its waters as an international resource.

Indeed, former EU Trade Commissioner Pascal Lamy, now a candidate to head the World Trade Organisation, in February proposed the Amazon should designated "global public goods" and be administered by the international community -- a proposal that drew a sharp rebuke from Brazilian government.

Brazil mounted a big Amazon exercise in November called Operation Ajuricaba involving 3,000 men, 35 planes and 170 boats. The enemy was a superior foreign military force.

"Brazilian armed forces planning for the hypothetical war in the Amazon region foresee the region turning into a new Vietnam," Correio Braziliense newspaper wrote. Diplomats also note with interest that Vietnam has just posted a defense attache to its embassy in Brasilia.

CONCERN OVER FOREIGN POWERS

"The internationalisation of the Amazon is one of the worries that takes us to this strategy of defence in relation to signs from big countries, not just the United States but also Europe," Gen. Figueiredo said. "We must be prepared. After all, the Brazilian Amazon is Brazilian."

In 2003, top government aide Jose Dirceu said: "If the United States occupies Colombia, it will occupy the Amazon."

A spokesman for the US Southern Command, which covers Latin America, said Brazil had every right to plan to defend territory but the United States posed no threat.

"I think its safe to say in Southern Command we don't maintain contingency plans for anything to do with Brazil," Lt. Col. David McWilliams said by telephone from Miami.

The two militaries' relations were excellent, he said.

Eduardo Gamarra, head of Latin American studies at Florida International University, also said military cooperation between the two countries was probably greater now than it had been for many years, for example with Brazil's leadership of the UN peacekeeping force in Haiti.

"We've been hearing rumours that the US is going to take over the Amazon for the water, to stop drugs. There are thousands of rumours like that," Gamarra said.

David Cleary of the environmental group Nature Conservancy in Belem said the military genuinely believed there was an international threat and that it was primarily American.

"The day-to-day threat comes from Colombia and Peru and not America," he said.