Obama on NSA data: 'The US is not spying on ordinary people'

US President Barack Obama has said he is ordering changes to the government's vast collection of phone records.

He pledged ''we will not monitor the communications of heads of state and government of our close friends and allies''.

In a speech in Washington, he said surveillance had helped US secure the country and its freedoms across the decades.

However he said there needed to be checks and balances to make sure the liberties of ordinary people were not sacrificed.