MONTEVIDEO (AFP) - Uruguay on Friday said that consumers can purchase up to 10 grams of marijuana per week at less than US$1 (S$1.25) per gram, as the country embarks on a unique experiment in drug regulation.

In December, the South American country became the first in the world to regulate the market for cannabis and its derivatives in what was considered a bold move by authorities frustrated with losing resources to fighting drug trafficking.

National Drug Board President Diego Canepa said buyers would have to register first under the decree, due to be signed by ministers on Monday and published Tuesday.

The government will call on private interests to plant cannabis "no more than two weeks after the decree enters into force," he added, noting that two to six licences would be issued.

Mr Canepa estimated that legal marijuana will be available in pharmacies for public consumption in December. The cannabis will be sold to the public at a price of 20 to 22 pesos (S$1.13) per gram.

"There are no state subsidies," said Mr Canepa, who added that the price was based on production costs and profits for the involved companies and pharmacies.

National Drug Board Secretary-General Julio Calzada said "the total volume consumed in Uruguay would be around 18 to 22 tons" of cannabis.

"Based on this, we need a maximum of 10 hectares to produce for this population of users."

Although it had not been illegal to use marijuana in Uruguay for decades, production and commercialisation of the drug had been illegal. The new regulations are part of an initiative by President Jose Mujica, a former guerrilla and doctor by training.