He said that the White House gives the NSA “policy direction”.
“But what we’ve seen over the last several years is their capacities continue to develop and expand, and that’s why I’m initiating now, a review to make sure that what they’re able to do, doesn’t necessarily mean what they should be doing,” he added.
A senior administration official also told Associated Press that the White House is considering ending its eavesdropping on foreign allies. The source added that the move was still under review, and that a final decision had not yet been made.
Ms Feinstein has previously backed the NSA, but she spoke out after reports based on new leaks from former NSA systems analyst Edward Snowden indicate that the NSA listened to Ms Merkel and other foreign leaders.
“With respect to NSA collection of intelligence on leaders of US allies – including France, Spain, Mexico and Germany – let me state unequivocally: I am totally opposed,” Ms Feinstein said.
She added that the US should not be “collecting phone calls or emails of friendly presidents and prime ministers” unless in an emergency with approval of the president.
The head of the NSA and other officials will appear before the House of Representatives later on Tuesday.