BRASILIA, Brazil, (AFP) — As tensions mount between Venezuela and Guyana, officials in distant Brasilia are watching their neighbours with increasing concern.

“If there’s one thing we don’t want, it’s a war in South America,” Brazilian President Luiz Inacio Lula da Silva said last week.

Lula has emerged as a peace broker of sorts, determined to prevent the current war of words over the disputed Essequibo region from escalating into something deadlier.

One of his closest advisors will take part in Thursday’s summit between Venezuelan President Nicolas Maduro and Guyana’s Irfaan Ali, in the Caribbean nation of St Vincent and the Grenadines.

Tensions have been rising ever since Caracas held a referendum December 3 on Essequibo, an oil-rich territory administered by Guyana for more than a century but claimed by Venezuela.

Venezuela’s appetite for the territory has been heightened by Guyana’s recent tenders for oil exploitation in the area, where huge deposits were discovered by US giant ExxonMobil in 2015.

– Strategic frontier –

The border between Brazil and the Essequibo territory stretches for around 800 kilometres (500 miles), along six Brazilian municipalities where 140,000 people live, including around 40,000 indigenous people, mainly in the Amazonian state of Roraima.

Venezuela and Guyana share around 700 kilometres (435 miles) of border, but this area is “almost entirely covered by jungle, offering neither the conditions necessary for the movement of troops with vehicles, nor the logistical support for an invasion,” Paulo Roberto da Silva Gomes Filho, an expert in military science, told AFP.

Venezuelan access to Guyana is much simpler via Brazil’s Roraima region: in the event of a ground offensive, the Venezuelan army would have to pass through Brazilian territory, he says.

But Brazilian Defense Minister Jose Mucio warned on Monday: “under no circumstances can we allow one country to attack another using our territory”.

Last week, Brazil announced it was reinforcing its troop presence in the Roraima and sending armoured vehicles there.

– Foreign military presence –

Brazil is concerned that the current crisis could lead to the presence of troops from other countries in the Amazon. The planet’s largest rainforest, most of which lies in Brazil, is an eminently strategic area, at the heart of global concerns over climate change.

The United States, an ally of Guyana, affirmed last week its “unwavering support” for Guyana’s sovereignty, and joint military air exercises were carried out last Thursday.

Caracas denounced the exercises as a “provocation” and accused Guyana’s Ali of having given his “green light” to the installation of US military bases in his country.

“What I fear most is that this crisis will set precedents for the presence of foreign bases and troops in the region… We’re talking about the Amazon, which is still of great concern to us,” Celso Amorim, Lula’s special advisor for foreign affairs, said in a recent interview.

– Lula as peace broker? –

Both Venezuela and Guyana had sought for Lula to be present at Thursday’s summit, but Brazil will be represented by Amorim, a former foreign minister. Brasilia gave no explanation for Lula’s absence.

Lula has pushed for a declaration by South American countries calling for a “peaceful solution” to the dispute, and warned his Venezuelan counterpart against any “unilateral measures” during a telephone call on Saturday.

Mauricio Santoro, an expert at the Brazilian Navy’s Center for Politico-Strategic Studies, believes that Brazil has an important role to play.

“Brazil is the biggest country in the region, and everything it does has a strong political and economic impact,” he says. “But to achieve a result, Lula will have to exert strong pressure on the Venezuelan government.”

Since his return to power in January, Lula has worked to break the international isolation of Maduro, whose regime is accused of human rights violations.