WASHINGTON — The FBI would gain broad authority to track the mail of people in terror investigations in a Bush administration proposal, officials said Friday, but the Postal Service is already raising privacy concerns about the plan.

The proposal, to be considered next week in a closed-door meeting of the Senate Intelligence Committee, would allow the bureau to direct postal inspectors to turn over the names, addresses and all other material appearing on the outside of letters sent to or from people connected to foreign intelligence investigations.

The plan would effectively eliminate the postal inspectors' discretion in deciding when so-called mail covers are needed and give sole authority to the FBI, if it determines that the material is "relevant to an authorized investigation to obtain foreign intelligence," according to a draft of the bill.

The proposal would not allow the bureau to open mail or review its content. Such a move would require a search warrant, officials said.

The Intelligence Committee has not publicly released the proposal, but a draft was obtained by The New York Times.

The provision is part of a broader package that also strengthens the bureau's power to demand business records in intelligence investigations without approval by a judge or grand jury.

The proposals reflect efforts by the administration and Senate Republicans to bolster and, in some ways, broaden the power of the bureau to fight terrorism, even as critics are seeking to scale back its authority under the law known as the USA Patriot Act.

A debate over the government's terrorism powers is to be begin in earnest at a session of the Intelligence Committee on Thursday, in what is shaping up as a heated battle over the balance between fighting terrorism and protecting civil rights in the post-Sept. 11 era.

The FBI has conducted mail covers for decades in criminal and national security investigations. But the prospect of expanding its authority to monitor mailings alarmed some privacy and civil rights advocates and caused concerns among postal officials, as well. They said the proposal caught them off guard.

"This is a major step," the chief privacy officer for the Postal Service, Zoe Strickland, said. "From a privacy perspective, you want to make sure that the right balance is struck between protecting people's mail and aiding law enforcement, and this legislation could impact that balance negatively."