The US National Security Agency (NSA) had considered winding up its mass phone surveillance programme well ahead of the leaks by whistleblower Edward Snowden about the project.

The Associated Press, citing current and former intelligence officials, reported that some officials believed that the secret programme's costs were too high, taking into account its limited counterterrorism benefits.

The internal debate in the NSA was kept in secret, as the NSA leaders strongly defended the programme following the leaks. Keith Alexander, then the NSA director, was also not aware about the proposal to kill the programme, the sources told AP. Two former senior NSA officials say they doubt Alexander would have approved it.

Snowden, a former NSA contractor, had leaked millions of classified documents to the media, revealing mass surveillance programmes of the NSA and the GCHQ such as phone tapping and snooping on internet activities.

The Obama administration faced severe criticism from across the globe as documents leaked by Snowden revealed that the NSA had tapped telephone conversations and spied on internet activities of prominent people, including German Chancellor Angela Merkel and Brazilian President Dilma Rousseff.

In response, Obama in January 2014 proposed that the NSA stop collecting the records, but he noted that legislation is required to adopt his proposal. As of now, the NSA continues to collect and store records of US phone calls, as Congress is yet to take up Obama's proposal.

AP noted that the behind-the-scenes NSA concerns could be relevant as Congress decides whether to renew or modify the phone records collection when the law authorising it expires in June.