“I’m a spray man myself,” President Bush told government leaders and American counternarcotics officials during his 2006 trip to Afghanistan. He said it again when President Karzai visited Camp David in August.

Mr. Bush meant, of course, that he favors aerial eradication of poppy fields in Afghanistan, which supplies over 90% of the world’s heroin. His remarks — which, despite their flippant nature, were definitely not meant as a joke — are part of the story behind the spectacularly unsuccessful U.S. counter-narcotics program in Afghanistan.

Mr. Karzai and much of the international community in Kabul have warned Mr. Bush that aerial spraying would create a backlash against the government and the Americans, and serve as a recruitment device for the Taliban while doing nothing to reduce the drug trade. This is no side issue: If the program continues to fail, success in Afghanistan will be impossible.

Fortunately, Mr. Bush has not been able to convince other nations or Mr. Karzai that aerial spraying should be conducted, although he is vigorously supported by the American ambassador, William Wood, who was an enthusiastic proponent of aerial spraying in his previous assignment, in Colombia. Mr. Wood, often called “Chemical Bill” in Kabul, has even threatened senior Afghan officials with cuts in reconstruction funds if his policies are not carried out, according to two sources.

But even without aerial eradication, the program, which costs around $1 billion a year, may be the single most ineffective program in the history of American foreign policy. It’s not just a waste of money. It actually strengthens the Taliban and Al Qaeda, as well as criminal elements within Afghanistan.

According to the U.N. Office on Drugs and Crime, the area under opium cultivation increased to 193,000 hectares in 2007 from 165,000 in 2006. The harvest also grew, to 8,200 tons from 6,100. Could any program be more unsuccessful?

The program destroys crops in insecure areas, especially in the south, where the Taliban is strongest. This policy pushes farmers with no other source of livelihood into the arms of the Taliban without reducing the total amount of opium being produced.

Meanwhile, there is far too little effort made against the drug lords and high-ranking government officials who are at the heart of the huge drug trade in Afghanistan — probably the largest single-country drug production since 19th-century China — whose dollar value equals about 50% of the country’s official gross domestic product.

There is a direct correlation between opium production and security. In relatively secure areas, production has dropped, but along the Pakistan border in the insecure south, production is increasing and amounts to about 80% of the overall crop.

Everyone talks about “alternative livelihoods” and alternative crops as the solution to the drug problem. This is true in theory — but this theory has been tried elsewhere with almost no success. Poppies are an easy crop to grow and are far more valuable than any other product that can be grown in the rocky, remote soil of most of Afghanistan.

Without roads, it is hard to get heavier, and less valuable, crops to market — and what market is there, anyway? It will take years to create the networks of roads, markets, and lucrative crops that would induce farmers to switch, especially when government officials, including some with close ties to the presidency, are protecting the drug trade and profiting from it. Any Kabul resident can point out where drug lords live — they have the largest and fanciest houses in town.

A leading expert on Afghanistan and a fellow at the Asia Society in New York and New York University’s Center on International Cooperation, Barnett Rubin, writes in a forthcoming study that “the location of narcotics cultivation is the result — not the cause — of insecurity.” He adds, “Escalating forced eradication” — as the U.S. Embassy wants to do — “will only make the effort fail more quickly because it actually builds the insurgency it is trying to eliminate.”

To be sure, breaking the narco-state in Afghanistan is essential, or all else will fail. But it will take years, and American policies today are working against their own objective. Couple that with the other most critical fact about the war in Afghanistan — it cannot be won as long as the border areas in Pakistan are havens for the Taliban and Al Qaeda — and you have the ingredients for a war that will last far longer than the war in Iraq, even if NATO sends more troops and the appalling National Police training program is finally fixed.

Solving this problem requires bold, creative thinking. Consideration should be given to a temporary suspension of eradication in insecure areas, accompanied by an intensified effort to improve security, build small market-access roads, and offer farmers free agricultural support.

When I offered these thoughts almost two years ago “Afghanistan: The Long Road Ahead,” [Oped, April 2, 2006], I was told by several high-ranking American government officials that I was too pessimistic. I hope they do not still think so. Even more, I hope they will reexamine the disastrous drug policies that are spending American tax dollars to strengthen America’s enemies.

Mr. Holbrooke is a former ambassador to the United Nations.