Increased defense spending by Venezuela, Brazil, and Ecuador, coupled with significant arms purchases by Chile and Colombia, may mark the start of an arms race in South America – a region that hasn't seen a major war between nations in decades.

"There is a real risk of it escalating and it could become very dangerous," says Michael Shifter, the vice president of policy at the Inter-American Dialogue in Washington.

Concern has grown in the wake of recent purchases by Venezuela and Brazil. Venezuelan President Hugo Chávez, flush with oil money, has spent freely on attack and transport helicopters, Russian fighter planes, and 100,000 Kalashnikov rifles.

In neighboring Brazil, which, with half of Latin America's landmass and population, President Luiz Inácio Lula da Silva recently asked Congress to allocate 10.13 billion reais ($5.6 billion) – a 53 percent increase – for its 2008 military budget.

Those increases came after Chile invested significant sums earlier in the decade. Colombia has received hundreds of millions of dollars in US drug-war aid for military purchases. And now Ecuador is also spending more on weapons.

"I think that it is done in different places for different motivations," says Mr. Shifter, who testified before the US Congress last year on the implications of Venezuela's increased military spending. "[Mr.] Chávez is using this as part of mobilizing the country and thinking of a possible attack from the US. In Chile, it is much more about giving the armed forces what they want. Colombia spends because a lot of the [US] aid comes in the form of military equipment."

The problem, continues Shifter, is that "there is tremendous mistrust between countries ... if you don't know what your neighbors' intentions are, then it is natural is to build up as much as you can to prepare for any contingency."

Some South American nations worry about Chávez's ambitions and do not want him to gain a significant military edge.

"Brazil won't say it, but Chávez's build up is what has made it invest in its military," says Reserve Col. Geraldo Lesbat Cavagnari, coordinator of the Strategic Studies Group at Unicamp university in São Paulo.

Brazil and Venezuela already vie for political supremacy in South America with Chávez bringing together the radical leftists under his socialist banner and President Lula leading a more measured coalition of social democrats. At this point, the two leaders are friends and the two nations have no border quarrels or historical feuds that could flare up. But there are tensions between Venezuela and Colombia over gas-rich territorial waters and border areas where Colombia's FARC guerrillas are active. And Veneuzela has made claims on the western part of Guyana.

But few people believe Chávez is buying weapons in order to attack a neighbor. He has warned opponents of his Bolivian ally Evo Morales that "rifle and machine guns will thunder" if they try to topple President Morales but Venezuela still does not have a military machine capable of shock and awe, analysts said.

In addition, its army is one-third the size of Brazil's, and distinctly less experienced and battle hardened than neighboring Colombia's.

Any attempts to settle territorial claims on western Guyana would give both the US and Britain, a former colonial power, reasons to enter the fray.

Yet the thought of an unpredictable leader with modern weaponry concerns some of the continent's moderates. Moreover, many analysts say the region cannot afford to devote large amounts of money to weaponry. Poverty is still a major problem in most South American countries and that – along with infrastructure, justice, and education – is seen as a more worthy priority than submarines or fighter planes.

"An arms race on our continent will oblige us to depart from the path of giving priority to investments in social programs," says Jose Sarney, a Brazilian senator and a fierce critic of Chávez. "Having a military power on the continent is dangerous for both Brazil and... Latin America."

Nevertheless, no one wants to get left behind, especially Brazil. Investment in modern weaponry, analysts agree, is long overdue for South America's biggest nation.

Years of neglect have left much of Brazil's war machine obsolete or in disrepair. Meanwhile, its priorities have changed from worrying about Argentina in the south to protecting its jungle frontiers on the north and west and its territorial waters that are home to sizeable new finds of oil and gas.

"There are very real security concerns that are being neglected," says Martin Joyce, the South America defense analyst for Jane's. "One is the Amazon region where drug traffickers are operating with impunity. Secondly, we are also seeing an increased presence of Colombian guerrillas, and that requires mobility and that is why we see helicopters and military airlift high on the priority list. Then there is the new oil reserves. Part of the reason for the procurement of a nuclear submarine is because they said they need to protect those resources. Venezuela comes fairly low down the list.".