The U.S. military is planning to send 20,000 troops into Afghanistan's main opium-growing region in order to choke off the drug money used to fund the Taliban insurgency, the New York Times reported April 29.

Commanders expect heavy fighting in Helmand, Kandahar, and Zabul provinces between the Marines and the Taliban, who are expected to strongly defend the opium crop that generates an estimated $300 million annually to pay for weapons, recruiting, and other needs. The Taliban also generate income by collecting protection payments from opium farmers, an arrangement that will be tested when the U.S. Marines move in.

"Opium is their financial engine," said Brig. Gen. John Nicholson, NATO's deputy commander in southern Afghanistan. "That is why we think he will fight for these areas."

Current rules of engagement prohibit NATO and U.S. troops from directly attacking people or targets involved in narcotics production unless they are assisting the Taliban, but Nicholson said that won't be much of a barrier to more assertive action in southern Afghanistan.

"We often come across a compound that has opium and I.E.D. materials side by side, and opium and explosive materials and weapons," Nicholson said. "It's very common — more common than not."

The campaign also will have an economic component, with the U.S. committing hundreds of millions of dollars for agricultural projects and infrastructure improvements. Opium now represents 60 percent of Afghanistan's gross domestic product, however, so getting farmers to stop growing poppies won't be easy.