The Uruguayan senate is to debate a bill that would legalise cannabis production from plant to pharmacy.

If passed, the historic bill would regulate production and the sale of cannabis for adults at a price of $1 per gram.The legislation was submitted by President Jose Mujica and approved by the lower chamber of the Uruguayan congress in July.

Given that pro-Mujica senators hold a majority in the upper chamber, the passing of the bill was regarded as a near certainty and would make Uruguay the first country in the world to legalise marijuana. Mujica, 78, said the legislation was a social experiment in the so-called War on Drugs and urged other countries to follow his example.

"We are asking the world to help us with this experience, which will allow the adoption of a social and political experiment to face a serious problem - drug trafficking," he said.

"The effects of drug trafficking are worse than those of the drugs themselves."

If the regulations fail, the government has pledged to reverse its decision, added Mujica.

A survey published in September showed that 61% of respondents did not approve of the measure.

The law has also raised eyebrows among Uruguay's neighbours, such as Brazil, who fear that Uruguayan cannabis may be increasingly trafficked into their country where marijuana is outlawed.

An opposition lawmaker, Gerardo Amarilla, demanded a referendum on the issue.

"Public perception, reflected in public opinion polls, is that this measure is the wrong way to address a serious problem," he said.

If passed, registered adults above 18 would be able to purchase up to 40 grams of cannabis a month from pharmacies and have the right to grow a maximum of six marijuana plants.