Man lances a poppy bulb to extract the sap, which will be used to make opium, at a field in the municipality of Heliodoro Castillo, in the mountain region of the state of Guerrero Thomson Reuters By Gabriel Stargardter

MEXICO CITY (Reuters) - Mexico's government has explored regulating poppy production to make pharmaceutical opiates like morphine in an effort to weaken heroin-smuggling gangs, according to two sources with knowledge of the government's thinking.

Amid a government review of drugs policy, Interior Minister Miguel Angel Osorio Chong asked policy experts late last year whether Mexico could win authorization from the International Narcotics Control Board (INCB), a United Nations body, to grow and export opium poppies for painkillers.

"It's a legitimate question," said one of the sources with direct knowledge of the talks, who was not authorized to speak publicly. "States have to ask themselves questions and have to discuss their policies."

It is not clear how seriously the government is considering the regulation of poppy production and it has not yet approached the INCB directly but the discussion illustrates how concerned it is about heroin-related violence.

Mexico's interior ministry did not respond to a request for comment.

On Thursday, Pena Nieto proposed legalizing marijuana-based medicines, substantially raising the amount of pot that users can carry and freeing inmates on minor marijuana charges.

With its shift, Mexico has joined a growing group of Latin American countries openly questioning the prohibitionist policies at the heart of the war on drugs.

"The terms of the drugs debate are changing in Mexico and the rest of the world," Pena Nieto said.

Pena Nieto made no mention of poppy regulation on Thursday, but in a speech on drugs at the U.N. General Assembly this week he said, "we should create productive alternatives in those areas where drugs are grown".

A heroin epidemic has killed tens of thousands of people in the United States in recent years and led to a surge in demand for Mexican heroin.

Regulating poppy production would in theory make it more difficult for Mexico's drug gangs to produce heroin, although some drug experts say Mexico's unique mix of extreme gang violence and weak institutions render the idea a non-starter.

More than 100,000 people have died in drug-related violence in Mexico in the last decade.

Last month, Mexican news magazine Proceso reported on a government study examining the legalization of opium for medicinal uses as a way to lower violence. The governor of the southwestern state of Guerrero, which has been ravaged by drug violence, has also floated the idea.

Click here for a graphic on opium poppy cultivation and murder rates in Mexico: http://tmsnrt.rs/1Wg49NR

Stefano Berterame, the INCB chief, said Mexico has not made contact over authorizing its opium crop for export, a prerequisite for major pharmaceutical buyers like Johnson & Johnson.

He said the INCB would likely refuse any request because there is a global surplus of pharmaceutical opiates, resulting in low prices. The INCB frowns on opiate gluts because they can easily be diverted into the illegal market.

Mexico could proceed without the INCB's blessing, as Portugal has previously done, to produce painkillers for its domestic market but it would struggle to offer poppy growers higher prices for their crop than those offered by drug cartels.

Peter Reuter, a drugs expert at the University of Maryland, said regulation would provide farmers with two markets, one legal and the other illegal, encouraging them to grow even more.

There is one precedent that could support the idea.

Under pressure from the United States, Turkey managed to destroy its illegal poppy trade in the 1970s by regulating production to make opium-based medicines.

"Turkey is indeed the poster child for this kind of policy," said Reuter. "It was a major producer for the illegal market and then converted entirely to the legal market."

However, he said Mexico's violent gangs, corrupt police forces and weak judicial system make it more comparable to Afghanistan, where attempts at poppy regulation never got off the ground, than Turkey.

(Reporting by Gabriel Stargardter; Editing by Simon Gardner and Kieran Murray)