US officials say Afghan President Hamid Karzai is partly responsible for the failure of poppy eradication efforts in Afghanistan, a US newspaper has said.
Afghanistan regularly supplies most of the world's demand for heroin
The New York Times cited a cable sent on 13 May from the US embassy in Kabul to Secretary of State Condoleezza Rice.
The cable said Mr Karzai - who has left for talks in the US - "has been unwilling to assert strong leadership" to curtail Afghanistan's heroin trade.
Afghanistan's drugs control minister told the BBC more could have been done.
Mr Karzai, meanwhile, has said he wants US concessions on key security issues.
Mr Karzai - who is due to meet President George W Bush on Monday - said on Saturday he would request the handover of all Afghan detainees in the US custody and also control over US military operations in Afghanistan.
The Afghan leader earlier also demanded action from the US after new details emerged of alleged abuse of prisoners by US troops in Afghanistan.
Mr Karzai's trip to Washington follows recent violent anti-US protests in Afghanistan triggered by claims in Newsweek magazine - now retracted - that US guards at Guantanamo Bay, Cuba, had desecrated the Koran.
The New York Times said the US cable said top Afghan officials, including Mr Karzai, had done little to overcome the resistance of Afghan provincial officials that was impeding the US-funded poppy eradication programme.
The cable said: "Although President Karzai has been well aware of the difficulty in trying to implement an effective ground eradication programme, he has been unwilling to assert strong leadership, even in his own province of Kandahar."
The Afghan minister in charge of counter narcotics efforts, Habibullah Qaderi, conceded to the BBC that the government could have done a better job at eradicating or cutting down opium poppy fields in many areas, in particular in Kandahar.
He said that lack of cooperation from the governor of Kandahar province - a close confidant of Mr Karzai - had been a factor.
The BBC's Andrew North in Kabul says most analysts there believe that, with parliamentary elections due in less than four months time, political pressures have held back some eradication efforts.
The US cable also criticised Britain for being "substantially responsible" for the failure to eradicate more poppy acreage in Afghanistan.
It said British personnel - who choose where the eradication teams work - had been unwilling to redirect efforts to the main growing areas.
The poppy flower produces opium, the source for heroin and morphine.
Afghanistan supplied more than 80% of the world's demand for heroin last year, according to the UN.
On Saturday, Mr Karzai demanded action from the US after new details emerged of alleged abuse of prisoners by US troops in Afghanistan.
He said he was shocked and would raise the issue with President Bush.
The soldiers involved in the deaths of two inmates and alleged abuse of others should be punished, Mr Karzai said.
The allegations are detailed by the New York Times citing a 2,000-page document leaked from a US army investigation.