Despite a last-minute concession by labor unions, the Senate refused Thursday to cut off a filibuster led by Sen. Orrin Hatch, R-Utah, against a bill that would ban employers from hiring permanent replacements for striking workers.

The Senate voted 55-41 to limit debate - five less than the required three-fifths majority needed. So Hatch and fellow Republicans are still free to essentially talk the bill to death every time it comes up for consideration.However, two union supporters - Sens. Al Gore Jr., D-Tenn., and Timothy Wirth, D-Colo. - were at the Earth Summit on Thursday, so Democratic leaders said they might try again next week.

Before the vote, Hatch - the ranking Republican on the Senate Labor Committee - continued his attack against the bill that he says "would stand a half century of U.S. labor law on its head." He said, "If an employer cannot hire permanent replacements during an economic strike . . . there is no incentive for unions to agree at the bargaining table. Striking becomes risk-free."

He added, "Under this legislation, an employer has only two choices: cave in and go broke, or don't cave in and go broke."

Meanwhile unions, in an effort to pick up support from some wavering Republican senators and southern Democrats, endorsed a weakening amendment by Sen. Bob Packwood, R-Ore.

It would allow employers who agree to federal arbitration to hire permanent replacements if unions reject recommendations from arbiters.

The House passed a similar striker replacement bill last July, but was 39 votes shy of the two-thirds majority needed to override a veto threatened by President Bush.