National Intelligence Director James Clapper told Congress on Tuesday it's "kind of a basic tenet" of U.S. intelligence-gathering to find out the intentions of foreign leaders.
He said it's done to make sure "what they are saying gels with what's actually going on" and to determine how allies' policies would impact the U.S.
Clapper also said allies have "absolutely" spied on U.S. officials.
He did not offer any specifics.
Recent reports show the National Security Agency had monitored the cellphone conversations of German Chancellor Angela Merkel. The White House is considering banning eavesdropping on friendly foreign leaders.
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