BOGOTA (Reuters) – Colombian President Juan Manuel Santos said on Monday the country's largest rebel group was increasingly selling its cattle to finance South America's longest-running insurgency as income from trafficking cocaine drops.

Colombia's Revolutionary Armed Forces of Colombia, or FARC, has been reeling from more than a decade of a U.S.-backed military offensive that has dealt it major blows and cut cocaine output in one of the world's top producers of the drug.

"The FARC is designing a complete strategy to counter the problem of lack of financing ... due to the blows to their funding sources, especially drug trafficking. One of the orders was to sell cattle to get more resources," Santos said.

The FARC has been trying in recent weeks to sell cattle stolen in other regions of the country, Santos said in a speech in the southern province of Caqueta.

The rebels have for decades funded their movement through control of coca production and have built up ties with drug gangs in some parts of the country and fought for control over key routes and supplies in others.