* Afghans welcome ban on private security firms
* U.S. concerned about effect on redevelopment work
* Image stained by deadly incidents in Iraq, Afghanistan
By Paul Tait
KABUL, Aug 18 (Reuters) - A ban on private security companies in Afghanistan could affect development and aid work as many of the firms guard Western projects in the country, U.S. officials said on Wednesday.
Afghan President Hamid Karzai issued a decree on Tuesday ordering private security companies to disband within four months -- part of an ambitious plan for the government to take responsibility for all security in the country from 2014.
The firms, who compete for billions of dollars in contracts, employ around 40,000 heavily armed guards -- mostly Afghans but including many foreigners. They are also used to guard convoys, embassies and other mainly Western interests.
Karzai has long been critical of the firms, saying they had caused horrific accidents, but the speed with which the decree was issued took some by surprise and U.S. officials in Afghanistan said they were still studying it.
"We are concerned that any quick action to remove private security companies may have unintended consequences, including the possible delay of U.S. reconstruction and development assistance efforts," embassy spokeswoman Caitlin Hayden said in a statement.
"Private security companies are currently filling a gap to allow us to deliver reconstruction and development assistance that, at the end of the day, focuses on improving the lives of the Afghan people," she said.
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The Pentagon on Tuesday described the deadline as "very challenging", but the move was welcomed by ordinary Afghans, for whom such firms have long been an irritant.
The heavily armed guards are a common sight on Afghan streets, forcing their way through traffic in convoys of four-wheel drive vehicles.
"They think they own the roads," said Edrees, a Kabul university student, who said ordinary Afghans were harassed by their macho behaviour and driving.
Mohammad Anwar, a Kabul shopkeeper, also agreed with the decision. "Karzai should have disbanded all the security firms earlier, whether Afghan or foreigners," he said.
Munir Mangal, Afghanistan's deputy interior minister, said Afghan officials would work with their international counterparts to ensure the smooth implementation of the decree.
"We are trying to implement a plan and I think we are working on a plan which would be practical," Mangal told reporters.
"We are not saying there will be no difficulties, but we should overcome those difficulties," he said.
The Afghan government tried unsuccessfully last year to formalise the market and log their weapons. Western officials said there were 52 registered private security companies, employing about 26,000 personnel, and many more unregistered.
The image of private security guards was deeply stained after a series of deadly incidents in Iraq, where it was not uncommon to see Western guards throw water bottles at pedestrians and cars to keep them away from the convoys they were guarding.
In the most notorious incident, security guards from U.S. firm Blackwater were involved in a shooting in 2007 in which 14 civilians were killed.
Blackwater has since changed its name to Xe and has several contracts in Afghanistan. In January, two U.S. security working for Paravant LLC, a unit of Xe, were arrested in Afghanistan on charges they murdered two Afghans in Kabul and wounded a third.
The U.S. State Department said last year it would review its use of contractors at overseas embassies after a scandal over sexual hazing by security guards at its Kabul mission.
Private security companies are subject to Afghan law but many Afghans still see them as operating with impunity. (Additional reporting by Sayed Salahuddin and Hamid Shalizi; Editing by David Fox) (firstname.lastname@example.org; Kabul Newsroom, +93 706 011 526) (For more Reuters coverage of Afghanistan and Pakistan, see: here) (If you have a query or comment on this story, send an email to email@example.com)