Washington: United States has lost critical foreign intelligence collection sources as a result of the unauthorized leaks created by Edward Snowden. This information is from a top American intelligence official.

According to him the leaks have done severe intellectual damage to the national security of United States and it is high-time to think about an alternative for such untoward incidents.

On the basis of such outcome, the US is beginning to establish changes in communications behavior of adversaries, particularly in terrorist related sources.

According US security sources, the recent threatening approaches by Russia might be due to the documents they have received from Snowden.