The US ambassador in Kabul has said that the driver of a military truck that crashed and killed several people will not be prosecuted in Afghanistan.
At least seven people died in rioting that followed the incident
The crash triggered the worst rioting in Afghanistan for years, with at least seven people killed.
Ambassador Ronald Neumann said the soldier could not be prosecuted in Afghanistan because a bilateral agreement prevented such action.
The Afghan parliament had called for the driver's prosecution.
The US military said that the 29 May incident was an accident caused by brake failure.
The military vehicle apparently lost control and smashed into at least 12 civilian cars during morning rush-hour in Kabul's northern suburbs.
People then started throwing stones and US troops opened fire on the crowd. Other reports said Afghan security forces also opened fire. At least seven people were killed.
US president George W Bush promised "a full investigation" into the incident.
Mr Neumann said a 2003 agreement between Washington and Kabul meant the soldier could not face legal action in Kabul.
One Afghan MP has already condemned the announcement.
Assadullah Hymatyar, a member of the lower house, told the BBC that the US military was not obeying traffic rules.
"Parliament will ask the Afghan government for the arrest of the agitators and criminals," he said. "And we will ask the government why they failed to control the situation."
Mr Hymatyar also criticised US forces for failing to respect Afghan culture when they carried out house searches and the searching of women.
He said that initially the demonstrations which followed the crash were peaceful, but "opportunists and others" used the situation to attack public property.
Meanwhile the UN has called on the Afghan government to introduce "fast reforms" of the police and judiciary.
The UN Special Envoy for Afghanistan, Tom Koenigs, said President Hamid Karzai must also ensure that warlords and their followers were disarmed.
He said that violence following last week's truck crash had caused "immense damage to the reputation of Afghanistan".
"We regret that the response of the police... was very weak and disappointing," he said.
"We think a professional and well-trained police is key to public security."
The UN envoy said that the riots were not necessarily anti-foreign. He blamed criminals and "anti-rich resentment".
On Saturday, President Karzai sacked dozens of senior policemen in what his office said was part of long-planned reforms.