Chairman of the Joint Chiefs of US Staff General Martin Dempsey said leaks by Security Agency whistleblower Edward Snowden will cost the Pentagon billions of dollars.

Chairman of the Joint Chiefs of US Staff General Martin Dempsey said leaks by Security Agency whistleblower Edward Snowden will cost the Pentagon billions of dollars.

The highest-ranking US military officer told a House Armed Services Committee on Thursday that the "magnitude of this challenge" might take a task force two years to determine the extent of the damage done by Snowden’s leaks.

"I suspect it could cost billions of dollars to overcome the loss of security that has been imposed on us," he said.

"We're working our way through that which we believe he has ex-filtrated," Gen Dempsey said. "And we have, I think, a fairly significant amount of knowledge in that regard.

Dempsey said the “vast majority” of the 1.7 million leaked documents were military-related and the Pentagon has established a task force to determine how the documents could be used and how to mitigate the problem. 

"The vast majority of [the pilfered documents] were related to our military capabilities, operations, tactics, techniques and procedures," he said.

US officials believe many of the documents that Snowden took were related to the country’s military capabilities, operations, tactics and procedures. They say less than ten percent of Snowden’s leaks were related to the National Security Agency’s surveillance program.

Snowden is wanted in the United States on espionage charges. He has given several interviews since last year on how the US government systematically monitors phone and internet data worldwide.