Legislation has been drafted to decriminalise cannabis on Jamaica, where the drug has been pervasive, but prohibited for a century.

The Caribbean island's justice minister Mark Golding told reporters that parliamentarians should make possession of two ounces or less a petty offence before the end of 2014.

He also expects decriminalisation for religious purposes to be authorised by then, allowing adherents of the home-grown Rastafarian spiritual movement to ritually smoke cannabis, which they consider a "holy herb," without fear of arrest.

Mr Golding said it will take longer to agree on more complex changes to Jamaica's Dangerous Drugs Act which would be needed to spur a medical cannabis research sector.

He said Jamaica, where scientists developed a cannabis-derived medication to treat glaucoma decades ago, is "well-positioned to be a forerunner" in efforts to research therapeutic uses of the plant.

As Jamaica advances decriminalisation, the government is committed to battling drug traffickers, Mr Golding stressed. He said keeping cannabis away from children, the international black market and organised crime will be a top priority.

Previous efforts to decriminalise the drug, or "ganja" as it is largely known in Jamaica, failed to advance because Jamaican officials feared they would violate international treaties and bring sanctions from Washington.

But those concerns have eased now that a number of nations and some US states have relaxed cannabis laws.

Mr Golding said the regulatory framework needed for a medical cannabis and scientific research industry in Jamaica is still being examined.

Setting maximum limits on cultivation is not anticipated, he said, but the government wants to ensure that small farmers "are not excluded and it does not just become something exclusively for major capital-intensive investors".