The leftist government announced plans last week to legalise the marijuana market as part of a drive to stop rising crime, arguing that the drug is less harmful than the black market where it currently trades.

The use of cannabis and other drugs is already legal in Uruguay, one of Latin America's safest countries and a trailblazer on liberal lawmaking. The reform being sent to Congress would legalise and regulate its sale and production.

Meeting the smoking needs of the nation of 3.3 million people will require annual production of about 27 tonnes, the government estimates, and the drug will be cultivated in a plantation of roughly 100 hectares.

It is not yet clear whether the drug would be grown by the state or by private contractors under license.

Planting should begin in September if the law passes Congress swiftly as expected - despite some opposition from rightist lawmakers, a government source said.

Harvesting would start six months later, said Julio Calzada, secretary general of the National Drugs Board.

"By regulating the marijuana market in the way we're proposing, we're going to undermine the development of trafficking of other drugs," Calzada said on Saturday. "Our inclination initially is to have production and regulation under state control."

The idea of a state-run chain of cannabis outlets has been ruled out and the drug would initially be sold by closely monitored private businesses.

Registered consumers would not be allowed to buy more than 30 grams per month and foreigners would be banned from buying the drug to prevent the small country becoming a hot spot for pot-smoking tourists, Calzada said.

Uruguay is a favorite holiday destination among Argentines and fashionable beach resorts like Punta del Este are also popular with visitors from neighboring Brazil.

"The idea is that it would only be sold to Uruguayans... the Netherlands has had to retrace its steps on that issue after years of difficulties with surrounding countries," Calzada said.

The famous coffee shops of Amsterdam have been a haven for drug tourism for decades, but new rules are coming into force that will make it harder for foreigners to buy.

Calzada said cannabis would carry a sales tax, the proceeds of which would fund rehabilitation programs for addicts. State-grown marijuana could also be used for medical purposes.