BOGOTA (Reuters) - Colombia's President Juan Manuel Santos on Tuesday signed a decree that legalizes medical marijuana, a move he says does not weaken the government's fight against illicit crops and drug trafficking.

The decree allows therapeutic use of marijuana, Santos said.

"Allowing the use of marijuana does not go against our international commitments to control drugs or against our policy of fighting drug trafficking," Santos told reporters after signing the decree.

Growing, distributing and selling cannabis remains illegal. The South American country suspended spraying of illicit crops this year, citing cancer concerns related to the herbicide glyphosate.

Current law allows possession of up to 20 grams of marijuana or 20 marijuana plants for personal use. A recent study showed 11.5 percent of Colombians have used marijuana at least once.

The government said some companies, including foreign ones, are interested in producing and selling cannabis. There are no plans to fully legalize marijuana for recreational consumption or commercial sale, however, unlike in Uruguay, which fully legalized it in 2013.

Colombia, long a hub for narcotics production and trafficking, was once home to large marijuana cultivations. Much of the crop was smuggled to the United States before drug cartels began producing the more profitable cocaine.

Austria, Belgium, Canada, the Czech Republic, Finland, Israel and some U.S. states already allow medical cannabis use.

Studies show marijuana can help treat pain and nausea and offers relief for sufferers of epilepsy and other conditions.

(Reporting by Helen Murphy and Nelson Bocanegra; Editing by Diane Craft)