Updated

CAMP PENDLETON, Calif. (AP) — U.S. forces are dealing a blow to the Taliban's multimillion-dollar opium business by securing deals with farmers to plant legal crops, The commanding general in charge of U.S. Marines in Afghanistan said Friday.

Maj. Gen. Richard Mills said during a video conference call at Camp Pendleton that farmers who own half of the poppy fields in Afghanistan's key poppy-growing area have pledged to not reseed next year.

Afghanistan supplies 90 percent of the world's opium, the main ingredient in heroin.

Curbing the Taliban's drug trade was a major goal when Marines seized the former insurgent stronghold of Marjah earlier this year. But troops have had to walk a fine line in their battle against the country's opium trade: If they destroy the crops, they lose the support of the population. Instead, they are encouraging local farmers to swap their poppies for legal crops, such as wheat.

During the spring harvest that just ended, more than 17,300 acres of poppies were swapped for legal crops around the farming community of Marjah, according to the Marine Corps.

"We've taken almost half of the poppy production land out of production," he said.

Explaining the stretegy, he added: "We offer them employment for money but we do not buy the drugs nor do we eradicate the drugs," Mills said. "We simply educate them and encourage them to find alternative means to gain a livelihood off the soil. We're getting good reception of that both at the local level and governmental levels."

It is hard to say whether farmers will keep their word given that opium prices are going up as a result of blight hurting Afghanistan's yield — which is likely to drop as much as 30 percent this year.

The blight, which turns the poppy plants black as they apparently rot from the inside, has hit about half of the crop growing in the northern part of Helmand province.

The higher prices could mean more money for the Taliban as well.

Efforts to discourage poppy farming have had mixed results, with the biggest progress in areas largely under government control.

Mills said troops recently seized almost five tons of raw opium headed out of the country to be sold for money to buy weapons and explosives for the Taliban.

Marines are not in the "drug interdiction business," Mills said, but "it's difficult to separate the two here. We target the Taliban, and the drugs are an addendum if you will."

He said NATO troops are making inroads in Helmand Province and slowly gaining support among the population. He said a hotline set up by coalition forces for people to provide anonymous tips about bombs or bomb builders has been getting about 20 calls a day.

U.S. Marines are training Afghan troops and police in preparation for President Obama's plan for local forces to take the lead in 14 months. Mills declined to say whether that deadline will be met.

"We are starting to see an Afghan army rise in strength and capability," he said, adding that police still have a long way to go.

Just under 20,000 U.S. Marines are in Afghanistan.

President Hamid Karzai, with money and assistance from foreign forces and donors, is in a race against the Taliban to convince people to turn away from the insurgency.

Success in Helmand, a province roughly the size of West Virginia, is considered key to strengthening Karzai's authority and promoting governance.

"I think this is going to be a critical year," Mills said, adding: "I think we've got some tough fighting in front of us."