The senator who introduced hotly debated legislation intended to shut down pirate websites said Thursday he is backing away from one of the most controversial parts of the bill, amid criticism from Web companies, human rights groups and Internet engineers.

Sen. Patrick Leahy, a Vermont Democrat, said he would recommend that "more study" be given to a provision in the bill that would give the U.S. attorney general new authority to seek court orders compelling Internet service providers to block the sites' domain names or Web addresses. A vote to bring the bill to the Senate floor for debate is scheduled for this month.

The bill, known as the PROTECT IP Act, is co-sponsored by more than 40 senators, a sign of broad support. It is backed by major Hollywood studios and other copyright holders that say the legislation is needed to combat foreign websites that sell access to pirated movies and counterfeit goods. (Among the studios advocating the legislation is Twentieth Century Fox Film, which like The Wall Street Journal is owned by News Corp.)

But since the bill's introduction last year, human rights groups and major Internet companies such as Facebook and Google have raised concerns about the First Amendment implications of shutting down entire websites, as well as potential technical problems that could arise from such blocking. A similar debate is taking place around the House version of the legislation, called the Stop Online Piracy Act.

Among the bills' most vocal critics: engineers who have worked on an Internet security system called "DNSSEC," which is intended to prevent hackers from using techniques that trick people into visiting malicious websites. During such attacks, hackers block the domain names of legitimate sites. The engineers say the problem with the PROTECT IP Act is that the security system can't distinguish between government blocking of pirated sites and blocking by hackers, so it wouldn't work and would leave people exposed to malicious attacks.