Every Sunday, counterinsurgency troops in combat gear march out of the army base in Pichari, a remote town with an incongruously wide avenue at the center of the world's No. 1 coca-growing valley.

It's a show of force in a region with a vibrant trade in the leaf used to make cocaine, and where Peru's government is trying to expand its presence and combat an illegal drug trade.

Coca is the lifeblood of the economy of this mostly rural municipality of 40,000 people. So much so that Pichari's central square features a sculpture of coca leaves.

For centuries, coca has been central to Andean culture and religion. But the mild stimulant chewed to fight off fatigue and altitude sickness has in recent decades become the focus of the illegal cocaine trade.

Pichari lies on the banks of the Apurimac river in a long valley that the United Nations says yields 56 percent of Peru's coca leaves. There is so much coca that growers sometimes dry the leaves on soccer fields and children frolic in them.

The government promises to soon begin eradication in the region known as the VRAE — the Valley of the Apurimac and Ene rivers. It has not specified when, although it is building 11 new military bases in the valley this year.

Peru last year displaced Colombia as the world's leading producer of coca leaf, the United Nations announced last month. But unlike Colombia, most cocaine produced in Peru is exported not to the United States but to Brazil, Argentina and Europe. Much is smuggled by air and land through neighboring Bolivia.

The Peruvian government's ambitious coca eradication plans are backed this year by $55 million in U.S. counterdrug aid.

But those plans could meet fierce resistance in towns like Pichari. That's due, in part, to a strong presence of Shining Path rebels, who along with local criminal syndicates live off the drug trade.

Rebels have killed nearly 100 government soldiers in the region since 2008. Government commandos in August killed two top Shining Path commanders in the area and last week arrested 23 people, some in Pichari, accused of crimes including conspiring with terrorism.