The office of the Director of National Intelligence said in a statement that the bulk telephony data -- the subject of leaks by former intelligence contractor Edward Snowden which shocked many in the US and abroad -- would be destroyed "as soon as possible" to comply with a law passed by Congress in early June.

The statement said that during the 180-day transition period required under the USA Freedom Act, "analytic access to that historical metadata... will cease on November 29, 2015."

But it added that "for data integrity purposes," NSA will allow technical personnel to continue to have access to the metadata for an additional three months.

The NSA must preserve bulk telephony metadata collection "until civil litigation about the program is resolved, or the relevant courts relieve NSA of such duties."

The data kept for litigation "will not be used or accessed for any other purpose, and, as soon as possible, NSA will destroy the Section 215 bulk telephony metadata on expiration of its litigation preservation duties."