Heavy US reliance on private security in Afghanistan has helped to line the pockets of the Taliban because contractors often do not vet local recruits and end up hiring warlords and thugs, Senate investigators said.
The finding, in a report by the Senate Armed Services Committee, follows a separate congressional inquiry in June that concluded trucking contractors pay tens of millions of dollars a year to local warlords for convoy protection.
Senator Carl Levin, chairman of the Senate panel, said he is worried the United States is unknowingly fostering the growth of Taliban-linked militias at a time when Kabul is struggling to recruit its own soldiers and police officers.
"Almost all are Afghans. Almost all are armed," Levin, a Democrat, said of the fleet of young men working under US contracts.
"We need to shut off the spigot of US dollars flowing into the pockets of warlords and power brokers who act contrary to our interests and contribute to the corruption that weakens the support of the Afghan people for their government," he said.
The Defence Department does not necessarily disagree but warns that firing the estimated 26,000 private security personnel operating in Afghanistan in the near future is not practical.
In recent months, US forces in Afghanistan pledged to increase their oversight of security contractors and set up two task forces to look into allegations of misconduct and to track the money spent, particularly among lower-level subcontractors.
The Defence Contract Management Agency has increased the number of auditors and support staff in the region by some 300 percent since 2007. In September, General David Petraeus, the top war commander in Afghanistan, directed his staff to consider the impact that contract spending has on military operations.
Military officials and Republicans on the Senate Armed Services Committee warn that ending the practice of hiring local guards could worsen the security situation in Afghanistan.
They say providing young Afghan men with employment can prevent them from joining the ranks of Taliban fighters, and bringing in foreign workers to do jobs Afghans can do is likely to foster resentment.