WASHINGTON DC – The National Security Agency has been secretly collecting phone call records of tens of millions of Americans, including calls made within the United States, according to reports.

USA Today reported that the NSA, which is in charge of a domestic spying program, has been building up the database using records provided by three major phone companies-AT&T, Verizon Communications and BellSouth-but that the program “does not involve the NSA listening to or recording conversations.”

The existence of an NSA eavesdropping program launched after the Sept. 11, 2001, terror attacks was revealed in December.

Defending the controversial eavesdropping program, President Bush and his administration officials have said it aims to uncover links between international terrorists and their domestic collaborators and only targets communications between a person inside the United States and a person overseas.

But USA Today said that calls originating and terminating within the United States have not escaped the NSA’s attention.

“It’s the largest database ever assembled in the world,” the paper quoted one source as saying. The agency’s goal is “to create a database of every call ever made” within U.S. borders, it said the source added.

The NSA has “access to records of billions of domestic calls,” USA Today said. Although customers’ names and addresses are not being handed over, “the phone numbers the NSA collects can easily be cross-checked with other databases to obtain that information,” it said.

Air Force Gen. Michael Hayden, who headed the NSA from 1999 to 2005 and was nominated by Bush as director of the CIA, would have overseen the call-tracking program, the newspaper said.

Among major U.S. telecommunications companies, only Qwest Communications International has refused to help the NSA program, the paper said.