Progressive Media Resources Group

The White House has declined to say whether Merkel's phone was monitored in the past. But according to the Wall Street Journal, the Obama administration ordered the NSA to cease the surveillance of her and other leaders after the program emerged over the summer in a separate, internal review of the agency's activities.

Carney said that internal review, led by the White House with input from agencies across government, will also also be completed before the end of the year. It contains what Carney described as a "separate" component dedicated to dealing with issues relating to "some of the very specific things with regard to intelligence gathered, including matters that deal with heads of states and other governments".

The external review, which will feed into the White House's internal assessment of surveillance, has itself been criticised for being too close to the Obama administration.