The Senate easily passed a measure Thursday expanding a powerful surveillance law, used in spy and terrorism investigations, to allow U.S. agents to wiretap lone foreigners who can't be linked to a terror organization or government.

Currently, U.S. law enforcement officers can get warrants authorizing intelligence-gathering wiretaps from a secret court, but only if they can establish a reasonable belief the target is an "agent of a foreign power " or group.

The bill, which passed 90 to 4, would amend the 1978 Foreign Intelligence Surveillance Act (search) to remove that requirement.

As used in the act, the term "agent of a foreign power" includes those controlled by governments, political organizations or terrorist groups. But lawmakers feared that this requirement could hinder the FBI when its investigators can't make such a link to a known terror organization or a foreign government.

The bill, introduced by Sens. Charles Schumer, D-N.Y., and Jon Kyl, R-Ariz., has become known in Washington as the "Lone Wolf" measure. It still must be passed in the House.

Proponents also have described the bill as the "Moussaoui fix" because investigators in the weeks preceding the Sept. 11 attacks were unable to establish any connection between Al Qaeda (search) and Zacarias Moussaoui (search), the lone defendant charged as a conspirator with the 19 hijackers. Without that link, FBI headquarters believed they could not get a warrant targeting him.

"This is a reasonable provision that deals with change in the post 9-11 world," Schumer said after the vote. "Even individuals are empowered by technology and can do huge damage here to the homeland."

Sen. Patrick Leahy of Vermont, ranking Democrat on the Judiciary Committee, criticized the bill as a "quick fix" that the FBI hadn't even sought.

"This is aimed at making Americans feel safer, but it doesn't make them safer," Leahy said.

Senators rejected 35-59 an amendment by Sen. Dianne Feinstein, D-Calif., that would have given federal judges more discretion when to approve such surveillance warrants against foreigners believed to be acting on their own.

Feinstein said the change sought by Schumer and Kyl goes too far because it gives federal prosecutors too powerful a tool with far less judicial oversight than traditional criminal wiretap laws.

In a compromise reached last week, the bill was changed to include a provision by Sen. Russell Feingold, D-Wis., requiring that the Justice Department report to lawmakers how often that "lone wolf" provision is employed.

Feingold said Thursday that he worried the Senate changes "may well result in FISA serving as a substitute" for traditional wiretaps, which are harder for prosecutors to obtain and include more civil rights protections for citizens.