BOGOTÁ, Colombia — Colombia just discarded a cornerstone of the American-backed fight against drugs, blocking the aerial spraying of coca, the plant used to make cocaine. Bolivia kicked out the United States Drug Enforcement Administration years ago and allows farmers to grow small amounts of the crop. Chile, long one of Latin America’s most socially conservative countries, is gathering its first medical marijuana harvest.
Across the Americas, governments are increasingly resisting the tenets of the United States-led approach to fighting drugs, often challenging traditional strategies like prohibition, the eradication of crops, and a militarized stance to battling growers in a fundamental shift in the region.
“For the first time in 40 years, there is significant pushback from Latin American countries, which endured much of the drug war’s suffering,” said Paul Gootenberg, a historian on Latin America.
In many ways, the resistance reflects the declining influence of the United States in Latin America and a sweeping sense that its methods to fight drugs in the region have failed.
“If you use the same tools for 50 years and the problem isn’t solved, something is not working right,” said Yesid Reyes, the justice minister in Colombia, which halted its aerial spraying program on Thursday.
But the shift comes at a time of changing attitudes and concerns in the United States as well.
Political figures in countries like Uruguay, which is cautiously regulating its own legal marijuana industry, are looking at American states like Colorado and Washington that have legalized the sale of recreational marijuana. Officials from Uruguay even insist that their controls are more stringent in some ways than Colorado’s.
The reasons Latin American countries are calling for an overhaul of drug policies vary from country to country, but they largely involve attempts to diminish the bloodshed from the drug trade and relieve prison systems strained by surging inmate populations.
Latin America’s emergence as a major drug market — Brazil now ranks among the world’s largest cocaine consumers — is also influencing the debate.
“The cost in blood and treasure from the drug war has been overwhelming,” said Bruce M. Bagley, a specialist on the Latin American drug trade at the University of Miami. “Leaders are looking at the militarized approach and saying they don’t want 40 more years of Colombian-like policies.”
But while there has been a lot of strong talk from Latin American leaders about the failures of the drug war and the need for a new approach, there has been little clarity in the region on the path forward.
Colombia is a case in point. Mr. Reyes was one of the government officials to suspend aerial spraying to kill or stunt the coca crop on Thursday, citing concerns that the herbicide used may cause cancer in humans.
Last month, Mr. Reyes gave a speech at the United Nations in New York in which he called for new approaches to the drug problem, advocating the decriminalization of drug use.
But he and his government have made no concrete proposals to put forward legislation to that effect.
In an interview, Mr. Reyes said that Colombia had achieved much success in the fight against drug traffickers and would not back off. He added that it might even resume spraying if it found a safer chemical, leaving it unclear what the government’s new strategies will be.
As part of its decision on Thursday, the government gave a panel of experts 30 days to come up with recommendations.
Colombia is one of the closest allies of the United States in Latin America, so its decision to stop aerial spraying was highly symbolic. The tactic was a central part of its American-backed antidrug effort, and Colombia’s decision was made over objections from Washington.
But once it was clear that Colombia would go its own way, Washington’s response was relatively muted, with American officials offering their public support.
The American reaction was a strong contrast to its approach in years past, when Washington would have been much more insistent, analysts said.
“I believe we’re at a transition point right now,” said William R. Brownfield, the American assistant secretary of state for international narcotics and law enforcement affairs.
As former American ambassador to Colombia, he spoke in favor of the coca spraying program before the Colombian government’s decision to end it. But he also said that the dialogue on drug policy in Latin America was a positive development.
“We are effectively in the middle of this discussion,” Mr. Brownfield said. “We should be talking about considering and where appropriate adopting moderate and reasonable reforms to international drug control policy.”
While crack cocaine plagued cities and fueled high homicide rates in previous years, American law enforcement authorities across the country face another challenge today —methamphetamines, prescription drug abuse and heroin — detracting from the traditional focus on cocaine.
“Cocaine is not the problem it was 20 years ago when crack cocaine was driving a lot of violent crime — we just don’t see that,” said Chuck Wexler, executive director of the Police Executive Research Forum, a law enforcement policy group.
Many Latin American countries are still trying to figure out what their new policies should be. Voters in the region have not particularly embraced the drive to legalize drugs. Politically, it is rarely a win.
“In Latin America, it is a fairly socially conservative society with respect to drug issues,” said John Walsh, an analyst with the Washington Office on Latin America, a research group. “The drug war and its propaganda has worked. It’s been going on for a long time. They see it as a Manichaean good versus evil, and talk about a regulated approach seems like a surrender.”
He added, “There is a lot of support among Latin American elites for a regulated approach, but the politics are forbidding.”
In Guatemala, President Otto Pérez Molina has repeatedly called for new strategies, saying he would consider creating legal, government-regulated markets for some drugs as a way of neutralizing the power of drug gangs. But he has made no concrete proposals.
President Enrique Peña Nieto of Mexico has said he is open to a debate on alternative approaches like legalization, but he has done little to propel discussions on it. Even in Mexico City, a progressive bastion in an otherwise conservative country, decriminalization efforts have faltered.
Mr. Peña Nieto came into office with a focus on improving the economy, playing down the country’s problems with drug gangs and organized crime. But in response to the violent attacks of criminal groups, he has largely adopted the approach of his predecessor, Felipe Calderón, going after the major drug groups by capturing or killing droves of their top leaders.
In Bolivia, President Evo Morales kicked out American D.E.A. agents in 2009 and even won an exception to a United Nations antidrug convention that acknowledges the right of Bolivia to allow traditional uses of coca.
He also has pushed ahead with a system permitting farmers to grow small plots of coca, which has been chewed as a mild stimulant for centuries and used for traditional medicinal and religious purposes.
Yet he has not joined calls for legalization of cocaine or other drugs, either.
Elsewhere in the region, there are mixed messages and conflicting policies.
In Peru, another major producer of cocaine, Congress is considering a law that would allow the armed forces to shoot down planes suspected of carrying drugs. That would reverse a policy banning such shoot-downs that went into place in 2001, after a plane carrying American missionaries was shot down by mistake and two Americans were killed.
Brazil passed a drug law intended to keep recreational drug users out of prison, substituting other measures like community service or education programs. But loopholes in the law have led it to have the opposite effect, and the number of people sent to prison in Brazil for drug offenses, including minor ones, has soared.
“There is no consensus in Latin America as to what drug policy should look like,” said Vanda Felbab-Brown, a senior fellow of the Brookings Institution. “What we are definitely going to see is countries increasingly adopting their own policies and experimenting with policies.”
Written by William Neuman and Simon Romero for The New York Times.