Critics say the alleged secret data collection is yet more proof of excessive domestic surveillance by the Obama administration.
The White House says the monitoring of telephone records of millions of Americans by the US National Security Agency (NSA) is a “critical tool” to fight security threats.
White House spokesman Josh Earnest defended a recent court order allowing the US government to secretly collect citizens’ telephone records, and said there is robust legal oversight of the programme.
He added that Congress has been fully briefed on the practise.