US to Purge Intel on Foreigners After Five Years

US spy agencies will expunge intelligence on foreigners gleaned from phone or email intercepts after five years, unless it has security value, according to a policy review released on Tuesday.

Two years after whistleblower Edward Snowden revealed a vast overseas digital dragnet that snared, among others, German Chancellor Angela Merkel, the US government said it is changing how it handles the trove of intel.

"We have imposed new limitations on the retention of personal information about non-US persons," the Office of the Director of National Intelligence announced.

"Now intelligence community elements must delete non-US person information collected through SIGINT five years after collection," it added, referring to signals intelligence, or the gathering of information from signals and other communication.

The review was requested by US President Barack Obama, who hosts German Chancellor Angela Merkel next week at the White House.

Mr Obama was reportedly unaware that the leaders of allied nations were being bugged, and ordered the practice to stop.

The shift brings retention of foreigners' data into line with existing rules for US citizens, but will likely be seen as not going far enough by privacy advocates.

"Our signals intelligence activities must take into account that all persons have legitimate privacy interests," said US Homeland Security and counter-terrorism Advisor Lisa Monaco.

"At the same time, we must ensure that our intelligence community has the resources and authorities necessary for the United States to advance its national security and foreign policy interests."