Afghanistan retook its place as the world's leading producer of heroin last year, after US-led forces overthrew the Taleban which had banned cultivation of opium poppies.
Production has surged since the end of the Taliban regime
The finding was made in a key drug report, distributed in Kabul on Sunday by the US State Department, which supports almost identical findings by the United Nations last week.
Low-grade heroin is refined in Afghanistan from opium, which is manufactured from the extract of poppies.
"The size of the opium harvest in 2002 makes Afghanistan the world's leading opium producer," the report said.
The International Narcotics Control Strategy Report said the area of land used to cultivate opium poppies reached 30,750 hectares, compared with 1,685 hectares in 2001.
Afghanistan overtook Burma - whose production fell for the sixth straight year, to 630 tonnes - as the leading opium producer.
The British government is the leading sponsor of the anti-drugs campaign in Afghanistan.
The report said fighting illegal drug trafficking was key to the US war on terrorism.
Production has surged since the end of the Taliban
"The US campaign against global terrorism in 2002 highlighted the importance of our international drug control programs," it said.
Despite its own figures showing the Taleban had cut Afghanistan's heroin production by about 95%, the report claimed that heroin had "financed the former Taleban regime".
The UN International Narcotics Control Board (INCB) report, released on 26 February, said that Afghanistan produced 3,400 tonnes last year, up from 185 tonnes in 2001.
While the US report praised US-backed Afghan president Hamid Karzai for the measures he has introduced to cut heroin production, the UN report said his two executive orders had no practical impact.
The Pentagon and the State Department are reportedly split over how heroin production should be tackled in the country.
The Taliban banned production
While the Pentagon insists that the military operations in Afghanistan should be limited to fighting terrorists, while the State Department thinks armed forces should tackle opium production.
The US report also praised Pakistan for "excellent" co-operation with US anti-drugs efforts.
Last week the head of Pakistan's Anti-Narcotics Force, Major General Zafar Abbas, said that heroin production in Afghanistan this year is expected to reach more than 4,000 tonnes.
Russian guards patrolling Afghanistan's 1,340-kilometre border with Tajikistan, the main transport route for Afghan drugs to European markets, have seized 1.5 tonnes of heroin already this year.
Last year, Russian and Tajik border guards seized 6.7 tonnes of drugs.