The US Defence Department says only a quarter of what it regards as key regions in Afghanistan support the government of President Hamid Karzai.
It says people support Mr Karzai's government in only 29 of the 121 Afghan districts considered most strategically important in the war effort.
In a 152-page report, the Pentagon said much of the population was either neutral to the Kabul authorities or supportive of the Taliban insurgency.
The BBC reports it blamed government corruption and lack of efficiency as the main reasons for people's distrust of Kabul.
Despite this, the Pentagon said opinion polls suggested Afghan people believed their security was improving.