The proposal to kill the program was circulating among top managers but had not yet reached the desk of Gen. Keith Alexander, then the NSA director, according to current and former intelligence officials who would not be quoted because the details are sensitive. Two former senior NSA officials say they doubt Alexander would have approved it.

Still, the behind-the-scenes NSA concerns, which have not been reported previously, could be relevant as Congress decides whether to renew or modify the phone records collection when the law authorizing it expires in June.

The internal critics pointed out that the already high costs of vacuuming up and storing the “to and from” information from nearly every domestic landline call were rising, the system was not capturing most cellphone calls, and the program was not central to unraveling terrorist plots, the officials said. They worried about public outrage if the program ever was revealed.

After the program was disclosed, civil liberties advocates attacked it, saying the records could give a secret intelligence agency a road map to Americans’ private activities. NSA officials presented a forceful rebuttal that helped shape public opinion.