The Colombian government and leftist FARC rebels resumed peace talks Thursday amid differences over coca cultivation, blamed by political leaders for drug-linked violence and killings.

As the negotiations got under way in Cuba after a three week break, the delegation chief for the guerrillas questioned the eradication of a plant he said has benefits for mankind.

"If we agree that coca and cocaine are not the same thing, it seems illogical that to put an end to drug trafficking we should eradicate a plant that can be beneficial to humanity," Ivan Marquez said.

"The coca leaf has been used for centuries to relieve hunger, thirst and fatigue, as a digestive aid and relaxant, and it has been proven by science to have nutritional and medicinal properties," he added.

Marquez is the second in command at the Revolutionary Armed Forces of Colombia (FARC), which has been in talks with the government for more than a year, aiming to end their near 50-year conflict.

Considered Latin America's longest-running insurgency, it has left hundreds of thousands of dead and displaced more than 4.5 million people.

"Cocaine has become a harmful narcotic that poses serious problems for public health on a global level," Marquez said, adding that drug trafficking was "not an exclusively Colombian, but an international problem."

Cracking down on drug trafficking should "not come on the backs of the weakest elements, consumers and farmers, while the main beneficiaries are the financial empires around the world," he said.

The Colombian government delegation maintained its policy of declining to comment at the start of a new round of talks. However, its chief said Wednesday that he foresaw a coca-free future for Colombia.

"We want agriculture without coca, we want our farmers to permanently abandon this cultivation that has brought nothing but violence, poverty and marginality," former vice president Humberto de la Calle said before leaving for the Cuban capital, Havana.

Drug trafficking is the third of five agenda points for the peace talks.

Two partial agreements were reached in May and November on two of the points -- rural development and the political participation of the rebels after a potential peace deal.

The FARC, Colombia's largest rebel group, has around 7,000 to 8,000 fighters.