full story : http://news.bbc.co.uk/2/hi/world/us_and_canada/10429981.stm
The director of the CIA, Leon Penatta, said the company's bid was US $26m less than its nearest rival.
The contract, worth $100m, is to provide security at US consulates in the cities of Herat and Mazar-e-Sharif.
Blackwater guards allegedly opened fire on unarmed civilians in Baghdad in 2007 killing 17 people.
In the wake of the killings, the company rebranded itself Xe Services.
The company ended its operations in Iraq in 2009, in line with a ban by the government.
The US government said in January 2009 that it would not renew the company's task orders.