The U.S. National Security Agency has developed a tool to analyze and map the intelligence it collects from computer and telephone networks, according to top-secret documents acquired by the British newspaper the Guardian.

James Clapper, the U.S. director of national intelligence [File photo: Xinhua]

The Guardian broke the news during the two-day meeting between Chinese President Xi Jinping and U.S. President Barack Obama in California and the news also comes amid the spying controversy involving U.S. Telecommunications giant Verizon.

James Clapper, the U.S. director of national intelligence, admitted to the Guardian that the National Security Agency has used the data mining tool, called Boundless Informant, to keep track of the systems of companies including Google, Facebook and Apple in order to spy on their customers' online activities.

The documents show that the U.S. government has developed a list of potential overseas targets for cyber-attacks in what is called the Offensive Cyber Effects Operations (OCEO) which "can offer unique and unconventional capabilities to advance U.S. national objectives around the world."

According to the Presidential Policy Directive 20, OCEO refers to "operations and related programs or activities … conducted by or on behalf of the United States Government, in or through cyberspace, that are intended to enable or produce cyber effects outside United States government networks."

The issue of cyber security took center stage at the recent summit meeting between presidents Xi and Obama, during which Obama wanted to put pressure on Xi over allegations of Chinese hacking. The Guardian's revelation has come at an embarrassing time for the U.S. side and will likely dent Obama's efforts.