The Obama Administration is considering ending spying on allied heads of state, a senior Administration official said, as the White House grappled with the fallout from revelations that the United States had eavesdropped on German Chancellor Angela Merkel.
The official said that a final decision had not been made and an internal review was still under way.
Yesterday, two previous champions of the National Security Agency changed their stances in a sign of the pressure building over the months-long spying scandal that has strained longstanding alliances.
Senator Dianne Feinstein, chairwoman of the Senate Intelligence Committee, called for a "total review of all intelligence programmes".
The California Democrat said that the White House had informed her that "collection on our allies will not continue". The Administration official said that statement was not accurate, but added that some unspecified changes already had been made and more were being considered, including terminating the collection of communications from friendly heads of state.
A Republican Congressman also now wants to scale back counter-terror laws he once championed, citing an overreach by the NSA.
James Sensenbrenner plans to offer legislation as early as today to overhaul the NSA. It mirrors a bill by Democrats on House and Senate judiciary committees and is gaining support from the wings of both parties.
In the past, Sensenbrenner voted to give more surveillance power to US government spies and railed against civil liberties advocates who warned about privacy abuses.
Now he says he is "appalled and angry" to learn the NSA is sweeping up millions of Americans' phone records. He says that goes far beyond the intent of the 2001 Patriot Act.
Feinstein said that while she was not informed about the spying on Merkel, her committee was informed of the NSA's collection of phone records. But she said she "was not satisfactorily informed" that "certain surveillance activities have been in effect for more than a decade".
Her statement follows reports based on new leaks from former NSA systems analyst Edward Snowden indicating that the NSA listened to Merkel and 34 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," Feinstein said. She said 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.
One NSA official told Foreign Policy in reaction to Feinstein's comments: "We're really screwed now."
The official added: "You know things are bad when the few friends you've got disappear without a trace in the dead of night and leave no forwarding address."
As a result of the spying allegations, German officials said yesterday that the US could lose access to an important law enforcement tool used to track terrorist money flows.
A top German official said that she believed the Americans were using the information obtained from Merkel to gather economic intelligence apart from terrorism.
The Spanish Government has expressed "serious concern" that eavesdropping had targeted as many as 60 million phone calls in a month.
"We recognise there needs to be additional constraints on how we gather and use intelligence," said Jay Carney, the White House spokesman.Telegraph Group Ltd, AP