London, October 25 In a new revelation, whistle-blower and ex-national Security Agency (NSA) contractor Edward Snowden has said the United States intelligence agency monitored the phone calls of 35 world leaders once the contacts were provided by an officer in a US Government department.

The leaked document notes that one unknown United States official handed over two hundred phone numbers, including those of the thirty five world leaders, none of whom is named, to the NSA, the Guardian reported .

The numbers provided by the govt official were instantly “tasked” for observing by the NSA.

The confidential note reveals that the NSA encourages senior officers of the govt to share their contacts in order that the agency may add the phone numbers of leading foreign politicians to their surveillance systems.

The revelation came simply after German chancellor Angela Merkel Wednesday accused the United States of sound her mobile, that may potentially further damage diplomatic relations between the United States and its allies.

The NSA memo suggests that such surveillance wasn’t isolated, because the agency routinely monitors the phone numbers of world leaders.

The memo, dated October 2006, was issued to employees in the NSA’s signals intelligence directorate (SID), and was titled ‘Customers will help SID get Targetable Phone Numbers’.

The memo obtained by the newspaper gave an example of how data collected from the United States officers who mixed with world leaders and politicians may help agency surveillance.

“In one recent case,” the memo notes, “a United States official provided NSA with two hundred phone numbers of thirty five world leaders … Despite the fact that the majority is probably available via open supply, the PCs (intelligence production centres) have noted forty three previously unknown phone numbers. These numbers and many others are tasked,” the leaked memo declared.