In the heart of Afghanistan's opium-farming area, police use red tractors to churn up a small field of young green opium plants in a large sandy desert.

Such action would have been inconceivable a year ago because of attacks from Taliban-linked gunmen protecting their share of the impoverished nation's illegal four-billion-dollar-a-year opium trade.

This year the drugs-linked rebels are better armed, Counternarcotics Minister General Khodaidad says, estimating roughly 100 million dollars they earned from guarding trafficking routes in 2008 went towards new weapons.

But so is the poppy eradication force at work on the field at Nad Ali in the southern province of Helmand: it arrived with a whole Afghan army battalion, the NATO military force in support.

About 100 metres (yards) away, military vehicles parked at even intervals face into the undulating desert, which seems empty but for a few compounds; Afghan soldiers and their US mentors are on the ground, scanning the horizon.

"They may want to penetrate our screen line and fight the poppy eradication force," Lieutenant Colonel Abdul Wahid from the Counter Narcotics Infantry Battalion said. "Our positions are strong and we are ready for anything."

The troops were called in after an onslaught of attacks last year that left dozens of policemen dead and caused police poppy eradication teams to retreat.

Efforts to destroy opium, a key part of a largely US-funded counternarcotics strategy, managed only 10 percent of the target last year, the minister admits.

The new battalion is being tested in a real hotspot where officials say the links between the drugs trade and Taliban insurgents are evident.

"Nad Ali is the most dangerous place," said Khodaidad on a visit to officially launch the force which moved in a week earlier.

"This area is almost controlled by the Taliban except the headquarters of the local district."

Formerly a bread basket, the district is now one of the main contributors to Helmand's opium output which amounts to two-thirds of Afghanistan's total.

The country produces more than 90 percent of the world's opium, making it the main source of the world's heroin.

And in Nad Ali, it is government land that has been taken over and used to run the illegal narcotics industry.

It is big business in a prosperous opium farming district where land reclaimed from the desert is well irrigated and thousands of migrant labourers are brought in for the harvest, a Western official said.

Resistance to efforts to stop the crop has been rising, he added, not authorised to allow his name to be used in the media.

The government this year expects insurgents to present "more difficulties with eradication because they have heavy weapons, they have mortars," Khodaidad said, adding machineguns, rocket-propelled grenades and even missiles to the list.

"They are gaining a lot of money from drugs, they are buying arms and ammunition," he says.

In the first week on the ground in Nad Ali, the police and army units supported by international troops and contractors recorded eight incidents, ranging from rocket fire on their base to three exchanges with gunmen targeting eradication teams.

In one case NATO warplanes had to be called in to scare off the attackers, the men said.

But the military protection enabled police to destroy nearly 800 hectares (nearly 2,000 acres) of opium, equal to about 70 percent of what was eradicated in the same area last year, officials say.

A drop in the ocean, perhaps -- Helmand last year had 103,590 hectares under opium cultivation, according to the United Nations Office on Drugs and Crime.

UNODC said in a January report that Helmand's opium growing may fall this year because prices have slid amid a glut in the market, dropping about 25 percent to about 85 dollars a kilogram (39 dollars a pound) this year.

Drought and fear of eradication could also play a part, it said.

Khodaidad also expects a drop, maybe 30-40 percent, but says it will be because farmers are heeding the government's anti-drugs message and some have agreed to switch to growing food in a time of rising wheat prices.

A good eradication campaign could push this even higher, he said.

And NATO's International Security Assistance Force, which has about 55,000 troops in Afghanistan, is giving greater support than ever and lending vital logistic and intelligence support to counternarcotics missions.

"We feel we are doing much better work than in the last years," the minister said.