Bill Clark | CQ-Roll Call Group | Getty ImagesAn embarrassing leak of highly classified Pentagon documents has endangered intelligence methods, exposed American strategy and undermined trust among U.S. allies, former defense department officials and intelligence experts tell CNBC. America's control over its most valuable secrets has been thrust into question amid the fallout from the most damaging intelligence leak since Edward Snowden's breach more than a decade ago. 'Devastating' for American alliesThe major security breach also contained intelligence gathering on American allies, including South Korea and Israel. "Our allies can't trust us … That's why the Middle East, they're talking to the Chinese. one American defense industry executive told CNBC, speaking anonymously due to professional restrictions.

---