As the hemisphere’s leaders gather in Colombia this week for the VI Summit of the Americas, their on-camera discussions will be dominated by perennial convention topics: poverty, cooperation, the need for roads. But behind closed doors, they are expected to tackle a more contentious issue: the narcotics trade.

The 40-year-old war on drugs has cost billions in treasure and countless lives, but has produced mixed results. Drug abuse rates in the United States have been virtually unchanged over the last decade, as dips in cocaine use have been offset by rising consumption of marijuana, heroin and methamphetamines. The United States has the highest overdose rates in the world — almost four times higher than Europe, according to the United Nation’s 2011 World Drug Report.

And while anti-drug efforts have managed to reduce coca cultivation in Latin America by about one-third over the last decade, global cannabis production remains unchanged.

The war on drugs has also sparked a real war for control of drug routes, turning Central America into the most dangerous region on the planet.

“What has been a complete failure is the idea that reducing the supply — that is, attacking the source countries in Latin America and putting so much law enforcement energy in the interdiction operation — would lead to a shortage in the consumption countries,” said Martin Jelsma, the coordinator of the Drugs and Democracy Program at the Transnational Institute in the Netherlands. “There is no way that someone can continue to argue that that is in any way effective.”

In addition to the violence, Latin America’s drug war has led to notoriously overcrowded jails, clogged court systems and corruption. And yet the region has resisted looking for alternatives, as the United States has publically threatened to punish ideological dissenters.

President Barack Obama didn’t address drugs or other issues after arriving in Cartagena, one of 33 leaders expected before Saturday’s start of the two-day meeting. Obama’s two nights in Colombia are seen as a vote of confidence for this nation, which has made huge security strides over the last decade. It will be the first time that a U.S. president has spent two nights in the country.

Most Latin Americans believe U.S. narcotics policies “makes their drug and crime problems worse,” the Inter-American Dialogue, a Washington-based research center, wrote in a recent report. “Secretary of State Hillary Clinton, while visiting Mexico, acknowledged that U.S. anti-drug programs have not worked. Yet, despite growing calls and pressure from the region, the United States has shown little interest in exploring alternative approaches.”

U.S. Attorney General Eric Holder told The Miami Herald that legalizing drugs is tantamount to legalizing murder to bring down the homicide rate.

“I do not support that,” he said. “I think the reality is that the United States certainly has a responsibility to help those countries where drugs are grown, where those cartels are located as we are doing in Mexico. But the United States also has a responsibility in reducing demand.”

Even so, the administration has set aside money for drug rehabilitation programs and specialized drug courts aimed at reducing demand. “The United States has that responsibility as the chief consumer of drugs in the hemisphere,” he said.

In the past, the calls for change have been easy to ignore. They came from Latin American advocacy groups, intellectuals and former presidents. The only sitting leaders to seriously question Washington’s approach were perennial antagonists like Bolivia’s Evo Morales and Venezuela’s Hugo Chávez.

Now, some of the United States’ staunchest allies are sounding the alarm.

Colombian President Juan Manuel Santos, who cut his teeth as minister of defense during the height of the drug war, says it’s time to have a regional discussion. Mexico’s Felipe Calderón, who has seen his country throttled by violence, says the United States needs to consider “market alternatives” — a codeword for legalization — to control the drug trade.

The debate went into overdrive last month when Guatemalan President Otto Pérez Molina, a conservative former general, held a summit of Central American leaders to analyze a series of proposals, including creating sanctioned routes that would allow the free flow of cocaine to the north without destabilizing nations caught in the middle; some form of decriminalization; and establishing a Central American court system to exclusively handle drug crimes.

These aren’t topics the United States is eager to address.

“This is an awkward [issue] for President Obama because it’s an election year and he is not going to want to make it appear as if he would radically change U.S. efforts to counter narcotics trafficking,” said Robert Pastor, the former national security advisor for Latin America and Caribbean under the Carter administration, and now a professor at American University. “This is not a good year to raise these issues.”

When planning for the summit began in earnest 10 months ago, drug policy wasn’t on the agenda. But amid pressure from Pérez, Santos and others, the topic was recently shoehorned into the schedule – albeit relegated to a closed door meeting away from the media glare.

“The big question is how much of the private dialogue will spill over into the public setting,” said Ethan Nadelmann, the executive director of the Drug Policy Alliance.

In those closed-door sessions, no one is likely to advocate outright legalization, he said. Most of the talk has centered on keeping small-time consumers from clogging jails and favoring treatment over prison terms.

But even small steps are vial, Santos told El Tiempo newspaper.

“The only thing we’re proposing is that we address the issue, because up until now many countries, including the United States, have refused to do so,” he said. “It’s been 40 years since the world got into this drug war, and I think we should analyze whether or not we’re doing the right thing.”

Some countries are already going it alone. Argentina’s legislature is considering a bill that would decriminalize drugs and cultivation for personal use. Uruguay has never criminalized possession of small amounts of narcotics and is drafting legislation to make those protections more explicit.

It’s in these modest unilateral efforts where governments can proceed with the “least international fallout,” Nadelmann said.

“It’s very unlikely that heroine, cocaine or methamphetamines will be legally regulated like alcohol or tobacco anytime soon,” he said. “It’s the prohibition of these drugs that is generating the horrific levels of crime and violence and black markets, but that option is not on the table.”

The United States isn’t the only country with a consumption problem. Over the last decade, Brazil has gone from being primarily a trans-shipment point to being the world’s No. 2 cocaine consumer, said Joao Augusto de Castro Neves, a Latin America analyst for the Eurasia Group.

Authorities have seen a spike in crack addicts, and the U.N. said cocaine seizures in the country tripled to 28 metric tons between 2004 and 2009. While the country has favored heavy police enforcement to deal with the problem, some experts said the ruling party is working on a decriminalization bill. But it’s unclear if such a measure would have popular support, de Castro said.

How Brazil, the hemisphere’s second-largest economy, deals with the issue could sway the rest of the hemisphere, Nadelmann said.

“The big question is Brazil,” he said. President Dilma “Rousseff has been fairly quiet and everyone is eager to get her opinion,” he said.

What seems clear is that as Latin America continues to emerge from the shadow of the United States, it will increasingly be willing to forge its own policies.

“Drugs are not going to disappear from the planet,” Jelsma said. “So we have to become more clever on how to manage the problem and how to deal with it in a way that does as little harm as possible.”

Miami Herald staff writers Mimi Whitefield and Jacqueline Charles contributed to this report