The US is considering ending its eavesdropping on friendly foreign leaders, confronted with a flood of revelations about its spying.
A final decision has not been made, according to one security source.
The administration is trying to repair damage from the months-long scandal – including the most recent disclosure that the National Security Agency monitored the communications of German Chancellor Angela Merkel.
President Barack Obama said the government was conducting “a complete review of how our intelligence operates.”
Senator Dianne Feinstein, chairwoman of the Senate Intelligence Committee, said the White House had told her that “collection on our allies will not continue”.
The security source said that 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.
Reports based on new leaks from former NSA systems analyst Edward Snowden indicate that the NSA listened to Mrs 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,” Ms Feinstein said.
She added that the US should not be “collecting phone calls or e.mails of friendly presidents and prime ministers “unless in an emergency with approval of the president”.
In response to the revelations, German officials said that the US could lose access to an important law enforcement tool used to track terrorist money flows.
Meanwhile David Cameron did not receive a USB stick reportedly used by Russia’s secret services to spy on world leaders at the G20 summit last month, Downing Street has said.
But No 10 did not rule out the possibility that officials were given one of the pen drives that is said to have contained a Trojan horse programme allowing sensitive documents stored on laptops to be accessed.
Italian media claimed yesterday that heads of state were given the devices at the acrimonious meeting in St Petersburg last month along with mobile phone recharging devices said to allow e.mails, text messages and telephone calls to be tapped.