The change allows Bolivian farmers to plant up to 22,000 hectares in coca, upfrom 12,000 under previous legislation.
Bolivia's first indigenous president is a former coca farmer who rose to powersupporting legalisation of the plant, which can be used to make cocaine but alsohas traditional uses in the Andes.
When chewed, coca leaves act as a mild stimulant and suppresses hunger, thirst,pain and fatigue. It is also used to make tea to fight altitude sickness.
Morales, a leftist leader who has allied with Venezuela's socialist government,expelled the US ambassador and Drug Enforcement Administration agents in 2008,accusing them of inciting the opposition.

President of Bolivia, Evo Morales, signs a new coco law advancing a progressive drug policy in La Paz, Bolivia Source: AAP
"Coca beat the United States," Morales said during a public event on Wednesdayas some coca farmers listened to his speech chewing on coca leaves.
Bolivia is a major cocaine transit and processing nation. Opposition lawmakerssaid they would sue to block the law, calling it unconstitutional because itbreaches international treaties. They said it would turn the Andean nation intoa free-for-all for drug dealers.