HAVANA, Cuba — When heads of state meet this weekend at the Summit of the Americas in Cartagena, Colombia, two contentious issues are expected to dominate the debate.

One will be Cuba’s exclusion from the meeting, since the Communist-ruled country isn’t a member of the Organization of American States (OAS), which organized the summit.

The other will be the growing backlash against the US-led drug war, including bold new talk of drug decriminalization.

Ironically, the two countries in the hemisphere that may be the most adamantly opposed to legalization efforts are Cuba and the United States.

But elsewhere in the region, more and more nations are losing patience with drug wars, as organized crime, corruption and savage violence spread, and security expenditures suck up public spending.

Several key US allies say the standard formula — military patrols in the streets, training and counter-narcotics aid from the United States — is faltering, so why not try something else? The push challenges one of Washington’s signature policy strategies for the region.

The movement is hardly the idle chatter of anti-American leftists. The most vocal legalization advocate in Latin America has been Guatemala’s conservative President Otto Perez, a retired army general and former head of military intelligence. He was joined at a meeting on the topic last month by Costa Rica’s centrist President Laura Chinchilla and Panama’s right-wing leader Ricardo Martinelli.

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Mexican President Felipe Calderon, the region’s most embattled drug warrior, has also encouraged a debate on legalization. In the Andean region, long-time US coca plant eradication efforts are taking criticism from Bogota to Bolivia.

Even Colombian President Juan Manuel Santos, who will host this weekend’s summit, has said that after 40 years of fighting drug cartels, he sees his country no closer to victory. Lawmakers in Colombia, the world's top cocaine producer, proposed allowing farmers to grow narcotic crops such as coca and marijuana.

Meanwhile, the countries that appear to be quietly siding with the anti-legalization camp are Washington’s historic rivals: Cuba’s Raul Castro and Nicaragua’s Daniel Ortega, onetime guerrilla fighters who toppled US-backed dictators.

Cuba, whose exclusion from the Cartagena summit has generated controversy for weeks, imposes some of the harshest criminal penalties in the hemisphere for drug possession and trafficking. US-Cuba cooperation on drug interdiction has been one of the few bright spots in their 50-year-old split, with Havana earning rare praise from the US State Department in the agency’s annual counter-narcotics reports.

Other Latin American nations appear to be leveraging the legalization issue to wrangle for more security aid from the US, saying they’re tired of allocating scarce resources to stop drugs that are primarily headed to American consumers.

Perez, the Guatemalan president, has even called for the US to pay countries in cash for the drugs they bust.

“For every kilo of cocaine that is seized, we want to be compensated 50 percent by the consumer countries,” said Perez recently, arguing it’s the US’s responsibility to pick up more of the counter-drug tab for the region’s poorest nations.

When US Vice President Joe Biden visited Mexico and Central America last month, he said he empathized with the region’s frustrated leaders, but he was categorical in stating the Obama administration’s plan to stay the course in the drug war fight.

“It is a totally legitimate debate,’’ Biden said. “But there’s no possibility the Obama-Biden administration will change its policy on legalization.”

Sanho Tree, a critic of US drug war strategy at the Institute for Policy Studies in Washington, DC, said he expects American officials at the Colombia summit to try squelching serious debate on alternatives to the status quo, in the interest of claiming that “legalization” was discussed but ultimately rejected.

“They love the false dichotomy of prohibition and drug war versus total anarchy and selling heroin in candy machines to children,” Tree said. “The goal, in my opinion, should be to begin a multi-year discussion about what a post-prohibition regulatory environment would mean to the region and the world.”

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Tree and others argue the economic incentives for drug cultivation and narcotics trafficking are simply too great to overcome in Latin America and other poor nations, and that increased seizures simply drive prices up further, producing new incentives.

By decriminalizing drug possession, strained criminal justice systems could place more attention on prosecuting more serious crimes, advocates say, and more public funding could be devoted to drug treatment.

But legalization efforts face plenty of skepticism from voters worried about rising drug use rates in countries that were formerly used as transit zones.

“There is no Latin American consensus that legalization is the solution,” said Michael Shifter, president of the Washington, DC-based policy forum Inter-American Dialogue. “But there is certainly agreement that the current, US-backed approach is not working — and that the drug problem is having adverse effects in many countries,” he said.