Obama to order the NSA to stop spying on leaders of US allies

US President Barack Obama is poised to order the National Security Agency to stop eavesdropping on the leaders of its allies, officials said, responding to a deepening diplomatic crisis.

The White House informed the Democratic Senator Dianne Feinstein of its plans, which grew out of a broader internal review of intelligence-gathering methods, prompted by the leak of NSA documents by a former contractor, Edward Snowden.

Feinstein, chairwoman of the Senate Intelligence Committee, said on Monday: "I do not believe the United States should be collecting phone calls or e-mails of friendly presidents and prime ministers."

Feinstein, a stalwart defender of the administration's surveillance policies, said her committee would begin a "major review of all intelligence collection programmes".

The White House said no final decision had been made on the monitoring of friendly foreign leaders. But the move would signal a landmark shift for the NSA, which has collected data on tens of millions of people around the world, from ordinary citizens to heads of state, including the leaders of Brazil and Mexico.

It is also likely to prompt a debate on what constitutes an American ally.