Under an accord that expires Oct. 1, the government allowed limited growing of coca even though Bolivian law bars growing the crop that is used to make cocaine.
The agreement between since-ousted President Carlos Mesa and growers has produced an uneasy peace in the Chapare region.
Coca growers, however, said they will fight if the government resumes efforts to thwart their operations, a subject likely to be a major issue in Bolivia's December presidential election, Knight Ridder news service reported.
Presidential candidates Evo Morales and former President Jorge Quiroga were nearly tied in a recent poll. Morales is a grower while Quiroga oversaw coca eradication efforts in 2001 and 2002.
The United States spent $150 million in four years in military and social aid -- in part to fight coca growing in Bolivia, which the U.S. State Department says is the world's third-largest producer of cocaine.