Lima, Peru ? Despite the world’s worst economic slump since the 1930s and projections that the number of poor in Latin America will rise this year, countries in the region have embarked on their biggest military spending spree in recent memory.

Recently, Venezuelan President Hugo Chavez visited Russia to purchase 500 combat helicopters for about $500 million, according to the Russian state-run RIA news agency. This would bring Venezuela’s purchases of Russian arms over the past five years to more than

$5 billion.

Days earlier, Brazilian President Luiz Inacio Lula da Silva welcomed French President Nicolas Sarkozy to the Brazilian capital and announced the start of final negotiations to purchase 36 French-made Rafale fighter jets, which, according to French officials, are likely to cost more than $7 billion.

In addition, Brazil is going forward with plans for the purchase and joint production of several other French weapons systems, including four Scorpene attack submarines, 50 military transport planes, and what would be Latin America’s first nuclear-fueled submarine.

Chile recently bought 18 U.S. combat aircraft, and announced plans to purchase U.S. long-range cannons and radars. Even Bolivia, one of Latin America’s poorest countries, has opened a $100 million line of credit to buy arms from Russia.

Peru, which has spent less than others in arms purchases, is watching all of this with growing anxiety. During my four-day visit here, hardly a day went by without big newspaper headlines about the increase in arms purchases by neighboring countries. Peru has a border dispute with Chile, which is under international arbitration.

“This trend is worrisome,” Peruvian Foreign Minister Jose Antonio Garcia Belaunde told me in an interview. “It’s hard to understand why countries are spending so much on arms purchases because this has traditionally been a peaceful region.”

Overall defense spending in Latin America and the Caribbean grew by 91 percent over the past five years, to $47.2 billion in 2008, according to the London-based International Institute for Strategic Studies.

The countries that most increased their military spending were Venezuela, Brazil and Chile, the group said.

What’s going on?, I asked several Latin American and U.S. officials. Isn’t this crazy, considering that just a few weeks ago the World Bank estimated that the number of poor in Latin America will grow by 6 million this year?

According to Garcia Belaunde, one possible explanation for the arms spending spree is the commodity bonanza of several Latin American countries in recent years, which has left them with substantial cash reserves.

This money is sometimes easier to spend on arms than on long-term infrastructure projects, he said. Many governments can’t launch ambitious development projects within the current fiscal year because they don’t have the technical means or enough time to put them together. So they may decide to buy weapons demanded by their armed forces, something that can be done much faster, he said.

Frank Mora, the senior U.S. Defense Department official in charge of hemispheric affairs, told me in a soon-to-be-broadcast television interview that — in the case of Brazil and Chile — the arms purchases are most likely aimed at modernizing military equipment that hasn’t been upgraded over the past 30 or 40 years.

“I don’t think that these purchases are an indication of an arms race,” Mora said, adding that more than 80 percent of the region’s arms over the past five years have been bought by just three countries, Venezuela, Brazil and Chile.

“But we have to continue looking at this carefully and avoid as much as we can the start of an arms race in what has traditionally been a peaceful region.”

My opinion: Granted, Latin America’s sky-rocketing arms purchases may be due to the commodities bonanza, and to the need to upgrade obsolete weapons. But I suspect that, especially in Venezuela’s case, there is an additional factor: corruption.

Based on Venezuela’s history of massive graft, and the Chavez government penchant for having emissaries coming and going with cash-filled bags, we can’t rule out that Russia is paying fortunes in commissions to top Venezuelan officials for its arms exports.

The tragedy for the region, in addition to the fact that countries should use much of that money to help reduce poverty at home, is that each nation’s arms purchases makes its neighbors nervous — and moves them to buy weapons themselves.

It’s time for a regional agreement to put a ceiling on arms purchases, and to stop a trend that — whatever its reasons — is insane.