AT&T has been working with the U.S. National Security Agency (NSA) since 2003, spying on Internet traffic andbeen forwarding 1.1 billion cellphone records per day, according to documents obtained by the New York Times.

The document, handed over by former NSA contractor Edward Snowden, described the decade-old partnership as "highly collaborative" and noted AT&T's "extreme willingness to help." The U.S. telecom giant even allowed the NSA to wiretap United Nations Internet communications and assisted in installing surveillance equipment on 17 of its Internet hubs in the country.

"This is a partnership, not a contractual relationship," read documents that remind NSA officials to be polite when entering AT&T's facilities.

The document didn't directly state AT&T as NSA's partner, instead it used code names. However, the cautious investigation of The Times and ProPublica led them to AT&T as the provider mentioned in the Fairview program. Several former intelligence officials also confirmed that it is AT&T that has been feeding NSA with 80 percent of the information.

It is not certain what AT&T is getting out of this partnership, but the document said that NSA spent $188.9 million on the Fairview program.

When asked to comment about the partnership, AT&T didn't directly answer to the allegation.

"We do not voluntarily provide information to any investigating authorities other than if a person's life is in danger and time is of the essence. For example, in a kidnapping situation we could provide help tracking down called numbers to assist law enforcement," AT&T spokesman Brad Burns told Reuters by email.

Aside from AT&T, Verizon was also mentioned in the document as NSA's new spy partner beginning 2013 under program Stormbrew.