Senator Rick Durbin: "If you measure [the compromise] against the original Patriot Act ... we've made progress [toward] protecting basic civil liberties at a time when we are dealing with the war on terrorism."

Democrat Harry Reid called the compromise "a step in the right direction."

The proposal would restrict federal agents' access to library records, one of the Patriot Act's most contentious provisions. A form of secret subpoena known as a National Security Letter could no longer be used to obtain records from libraries that function "in their traditional capacity, including providing basic Internet access." But libraries that are "Internet service providers" would remain subject to the letters.

The Senate proposal would no longer require National Security Letter recipients to tell the FBI the identity of their lawyers.

The compromise bill also addresses "Section 215 subpoenas," which are granted by the Foreign Intelligence Surveillance Act court. Recipients of such subpoenas originally were forbidden to tell anyone about the action. The proposed Senate measure would allow them to challenge the "gag order" after one year, rather than the 90-day wait in earlier legislation.