The D.E.A. declined to comment on the call-tracing program, except to say that it “exercises its legal authority” to issue administrative subpoenas. The N.S.A. also declined to comment on it.

In a separate program, N.S.A. officials met with the Qwest executives in February 2001 and asked for more access to their phone system for surveillance operations, according to people familiar with the episode. The company declined, expressing concerns that the request was illegal without a court order.

While Qwest’s refusal was disclosed two months ago in court papers, the details of the N.S.A.’s request were not. The agency, those knowledgeable about the incident said, wanted to install monitoring equipment on Qwest’s “Class 5” switching facilities, which transmit the most localized calls. Limited international traffic also passes through the switches.

A government official said the N.S.A. intended to single out only foreigners on Qwest’s network, and added that the agency believed Joseph Nacchio, then the chief executive of Qwest, and other company officials misunderstood the agency’s proposal. Bob Toevs, a Qwest spokesman, said the company did not comment on matters of national security.

Other N.S.A. initiatives have stirred concerns among phone company workers. A lawsuit was filed in federal court in New Jersey challenging the agency’s wiretapping operations. It claims that in February 2001, just days before agency officials met with Qwest officials, the N.S.A. met with AT&T officials to discuss replicating a network center in Bedminster, N.J., to give the agency access to all the global phone and e-mail traffic that ran through it.

The accusations rely in large part on the assertions of a former engineer on the project. The engineer, who spoke on the condition of anonymity, said in an interview that he participated in numerous discussions with N.S.A. officials about the proposal. The officials, he said, discussed ways to duplicate the Bedminster system in Maryland so the agency “could listen in” with unfettered access to communications that it believed had intelligence value and store them for later review. There was no discussion of limiting the monitoring to international communications, he said.

“At some point,” he said, “I started feeling something isn’t right.”

Two other AT&T employees who worked on the proposal discounted his claims, saying in interviews that the project had simply sought to improve the N.S.A.’s internal communications systems and was never designed to allow the agency access to outside communications. Michael Coe, a company spokesman, said: “AT&T is fully committed to protecting our customers’ privacy. We do not comment on matters of national security.”