America's top-ranking military officer says it will take two years and possibly billions of dollars to overcome the harm done by Edward Snowden's intelligence leaks.
Since last year, news organisations have published dozens of stories based on the documents leaked by Mr Snowden, who was contracted to work for the National Security Agency.
He faces spying charges in the US, but has been given asylum in Russia, the BBC reports.
Martin Dempsey, who chairs the joint chiefs of staff, says a mitigation task force had been established to investigate the extent of Mr Snowden's theft and to determine how to overcome it.
General Dempsey says the vast majority of documents taken were military-related and suspects it could cost billions of dollars to overcome the loss of security.