"This campaign is a long-term, time-consuming campaign," Karzai said, The New York Times reported Friday.

"It is not to be done in one or two years. It is related directly to the economy of the country. It is related directly to bringing peace in our country."

The Afghan leader responded to accusations by former U.S. State Department official Thomas Schweich in a New York Times Magazine article posted on the Web this week, the report said.

"What he said is his own idea," Karzai told The Times. "He criticizes the American government, Britain, (NATO's International Security Assistance) forces and the Afghan government."

The BBC quoted Schweich as saying Karzai had protected drug lords for political reasons and tolerated "a certain level of corruption" rather than lose power.

Karzai told reporters his government had eradicated or greatly reduced drug production in more than half the country's provinces, the BBC reported.

But Schweich told the BBC the claims ignore reality.

"The poppy cultivation right now is up and around 200,000 hectares, that's the biggest narco-crop in history," he said.