© Baz Ratner/ReutersA U.S. Army officer walks through a poppy field in Zharay district in Kandahar province, Afghanistan on April 26.
For years, American officials have struggled to curb Afghanistan's opium industry, rewriting strategy every few seasons and pouring in more than $6 billion over the past decade to combat the poppies that help finance the insurgency and fuel corruption.

It is a measure of the problem's complexity that officials can find little comfort even in the news this month that blight and bad weather are slashing this year's poppy harvest in the south. They know from past seasons that blight years lead to skyrocketing opium prices and even greater planting efforts to come.

"Now I am desperate, what can I do?" said Mohammed Amin, a poppy farmer in Tirin Kot in Oruzgan Province, who harvested only one kilogram of opium poppy this year compared with 15 last year. "I don't have any cash now to start another business, and if I grow any other crops, I cannot make a profit."

The seemingly unbreakable allure of poppy profits - for producers and traffickers, government officials and Taliban commanders alike - has kept fighting opium at the heart of efforts to improve security. It drove Richard C. Holbrooke, later the special envoy to Afghanistan, to write in 2008: "Breaking the narco-state in Afghanistan is essential, or all else will fail."

That concern is no less serious today, on the eve of the departure of thousands of American troops. But even as American leaders continue to emphasize the importance of the anti-opium effort, some officials are privately conceding that there is little chance for its large-scale success before the end of the NATO military mission in 2014.

The withdrawal is one worry. As the money from the Western military and civilian aid programs dwindles, the relative importance of opium to the economy is likely only to increase, said Jean-Luc Lemahieu, the director of the United Nations Office on Drugs and Crime in Afghanistan.

"Some money is available through the licit economy, but less than in the past as the Western contracts dry up, and so the importance of the illicit, informal economy will increase: human trafficking, gems, timber and weapons smuggling, and of course narcotics is a huge chunk of it," he said, adding: "The prognosis post-2014 is not a positive one."

Opium poppy, much like the coca grown in Colombia and Peru, poses a number of problems because there is so much money to be made that powerful political players, from police chiefs to governors, inevitably want a cut. The Taliban also support the drug trade, directly by protecting opium farmers, and indirectly by shielding traffickers, who pay off everybody in order to move their products quickly to the borders, according to narcotics experts at the United Nations and the Afghan government.

"Drugs are not the only priority issue for Afghanistan," said William R. Brownfield, the State Department's assistant secretary for international narcotics and law enforcement, in an interview this month. "But by the same token, if you do not address the drug issue you will not succeed in the other security, stability, democracy, prosperity objectives you are aiming for."

Despite all the effort, there are many troubling indicators. Nationwide, the number of poppy-free provinces, which reached a high of 20 in 2010, has now dropped to at least 17 and could be found to be still lower once researchers finish surveying remote provinces. Overall acres under poppy cultivation began rising again in 2009 after a significant drop the year before, and the total has grown slowly but steadily since.

Interdiction, while somewhat improved under new Afghan counternarcotics leadership, nets only about 3.5 percent of the 375 tons of heroin that leaves the country every year, according to the United Nations.

Even the success stories are unlikely to be sustainable, officials say. The prime example is the combined American and British counternarcotics campaign in the Helmand River Valley, in the heart of the province that produces nearly half of Afghanistan's opium. Since its start in 2009, the military mission has coincided with a 33 percent decrease in opium poppy cultivation in the area, and concurrent programs to create alternative jobs and crops have had a significant effect there.

But the troops are leaving - as many as 14,000 American Marines could depart Helmand by the end of the year - and many of the incentive programs are closing down unless Afghanistan's counternarcotics minister can persuade the West to renew them.

"We have to watch the answer develop over the next 6 to 12 months," Mr. Brownfield said, speaking of the effects of the military withdrawal. "That's what transition is all about - we're changing from a known to an unknown."

This year's low opium harvest has thrown another element of unpredictability into the picture. It has already driven a few farmers to commit suicide and others to flee because they feared retribution from creditors, according to the governor's office in Helmand. But rather than serving as a disincentive, the poor crop is more likely to prompt many to plant even more poppy next year to make up for this year's losses. That was the pattern in previous blight seasons, like 2010.

Mr. Amin, the poppy farmer in Tirin Kot, says that despite the risks, there is nothing to replace opium: "The poppy is always good, you can sell it at any time. It is like gold, you can sell it whenever and get cash."

In the meantime, the price for opium at the farm gate has soared - up more than 50 percent from a month ago and now selling for more than $320 per kilogram - another factor likely to spur more planting, Mr. Lemahieu said. Traffickers, who stockpile opium from year to year, are making a killing, he said.

On the Afghan side, the minister for counternarcotics, Zarar Ahmad Muqbel Osmani, has increased poppy eradication efforts in areas where farmers can grow other crops and is lobbying to expand the alternative crop program. But he remains deeply frustrated with the overall lack of law enforcement. Asked what it would take to affect the country's drug problem, he answered tersely, "Political will."

Among the continuing problems with corruption: information leaks that scuttle potential drug raids; political pressure that results in the release of major traffickers; and local politicians and police officers who participate in the poppy trade and use eradication programs to attack their rivals.

The deputy interior minister for counternarcotics, Lt. Gen. Baaz Mohammed Ahmadi, said his specialized force must still answer to local police officials.

"Because they are dependent on the regular force for everything, for gas for their vehicles and for the vehicles, even a very junior fuel dispatcher will know about the details of our operations," he said. "And when we plan an operation, we have to have approval of the local police chief or his deputy or the zone police chief, and if one of those people is corrupt or linked to a big trafficker, it leaks."

The Americans have taken at least three different tacks to fighting opium poppy cultivation.

In the early days after the 2001 invasion, a little more than half the current acreage was under cultivation, a legacy in part from the Taliban's ban on opium, which they ignored selectively. The Western emphasis was on driving the remaining Taliban fighters from the country, and with that in mind the Americans made allies of many of the old warlords who were also involved in the drug trade, entrenching a culture of impunity.

In 2005, British forces found nearly 20,000 pounds of opium in the office of the Helmand governor, Sher Mohammed Akhundzada, an ally of President Hamid Karzai. He was forced out at the behest of the British, but was later named to the Senate.

In 2006, as Americans began promoting eradication by specially trained Afghan forces, heroin was found in a car belonging Hajji Zaher Qadir, whom Mr. Karzai had been considering to lead the border police force. That appointment was scrapped, but Mr. Qadir is now one of the leaders in the lower house of Parliament. Many of the northern power brokers are also believed to be involved in the drug trade.

In 2007, as poppy growth reached a record-high 477,000 acres, the new American ambassador, William B. Wood, began to lobby for aerial eradication of the kind that had been undertaken in Colombia.

Mr. Wood became such a vocal proponent that he was known in the British press as "Chemical Bill." He once even tried to overcome President Karzai's skepticism about spraying by offering to publicly sit in a vat of pesticide clad only in a Speedo bathing suit to prove the chemicals were safe, said a Western official familiar with the discussions at the time.

Strenuous opposition from Mr. Karzai, European diplomats and some American policy makers stopped the program from getting off the ground. They feared it would backfire by reminding impoverished Afghans of Soviet-era spraying and would push them further into poverty, and into the arms of the Taliban.

In 2009, with the arrival of President Obama's team, including Mr. Holbrooke, Gen. Stanley A. McChrystal and later Gen. David H. Petraeus, the focus turned toward a counterinsurgency strategy that hinged on gaining acceptance from local Afghans.

Aware of how eradication deeply alienated rural Afghans who depended on opium for their families' subsistence, the American military distanced itself as much as possible from destroying poppy crops, instead supporting alternative crops and livelihoods. The State Department paid provincial governors to use Afghan forces to eradicate.

At the same time, officers from the Drug Enforcement Administration and the Justice Department mentored the Afghan police in interdiction and Afghan lawyers and judges in prosecuting narcotics cases.

The efforts have led to two perceived success stories: new drug courts, and the alternative crops and jobs effort in Helmand Province. Both initiatives have taken several years to mature. The drug courts, in particular, are widely viewed as largely insulated from corruption and are efficient, handling 635 cases in 2011. A few of them involved government employees, including police officers who were smuggling heroin. In the vast majority, the prosecutors obtained convictions.

Still, for many Afghans in the poppy belt, the idea of placing a bet on the government's future by cultivating anything other than poppy seems like one of the longest of shots.

"It is not an easy choice to grow poppies," said Tahir Khan, a local village leader in Khogyani district in the Nangarhar Province in eastern Afghanistan. "We know the danger and threat from the government and it is difficult, it needs hard work to recoup our investment. But the people are poor, they have no choice."