CHICAGO — A bill to bust Wisconsin's public workers unions that sparked mass protests and led Democratic lawmakers to flee the US state was set for approval on Thursday after a Republican legislative maneuver.

Republican state senators appeared to end the weeks-long standoff by stripping all references to the budget from the bill, which allowed it to pass without the legislative quorum required for fiscal measures.

The bill was to be taken up by the Republican-led state Assembly -- which approved a similar previous measure -- at 11:00 am (1600 GMT) on Thursday.

Wednesday's maneuver came a week after legislators in Ohio stripped public workers of most of their collective bargaining rights and as several other Republican-led state legislatures consider similar bills.

Critics say the legislation is part of a larger power grab by Republicans who aim to undermine unions -- a major source of grass-roots support for Democrats -- in key swing states ahead of the 2012 presidential election.

Wisconsin's Republican Governor Scott Walker has insisted the only way to close the state's yawning budget deficit is to eliminate collective bargaining rights so public workers cannot fight pay and benefit cuts.

"Beyond balancing budgets, our reforms give schools -- as well as state and local governments -- the tools to reward productive workers and improve their operations," he wrote in on op-ed for the Wall Street Journal on Thursday.

"Most crucially, our reforms confront the barriers of collective bargaining that currently block innovation and reform."

Tens of thousands of people descended on the capitol in daily protests insisting that they were not fighting over money but to protect their democratic right to form a union.

Walker acknowledged the protests, but said "their voices cannot drown out the voices of the countless taxpayers who want us to balance our budgets and, more importantly, to make government work for each of them."

Walker began sending layoff notices to 1,500 state workers last week and has ordered state police to arrest the 14 Democratic senators who fled to Illinois on February 17 to prevent the necessary legislative quorum to pass the bill.

Democrats blasted the move and said it will spur efforts to recall Walker and some of the Republican senators.

"The people I don't think knew what they were getting when they voted last November, so there will be a do-over" Senate Minority Leader Mark Miller told the Milwaukee Journal Sentinel.

"I think it's political suicide," added Democratic state senator Bob Jauch.

The Republican leaders left the legislature without speaking to reporters as protesters chanted "shame".

State Senate Majority Leader Scott Fitzgerald put out a statement saying Republicans were forced to act because the "childish stunt" staged by Democrats prevented the majority from pressing ahead with its agenda.

"The people of Wisconsin elected us to do a job," he said. "They elected us to stand up to the broken status quo, stop the constant expansion of government, balance the budget, create jobs and improve the economy."

The Republican attempts to bust public unions face strong opposition and have galvanized Democrats and union organizers.

A poll released last week showed that Americans oppose weakening the bargaining rights of public workers by a margin of 60 percent to 33 percent.

The New York Times/CBS News poll found that 56 percent opposed cutting the pay and benefits of public employees while 37 percent supported cuts.

Unions have seen their power and membership rolls shrink as the manufacturing sector has declined and shifted to anti-union southern states, and now represent just 12 percent of US workers.

Public workers account for more than half of union rolls, even though a dozen states prohibit state employees from forming unions.

Some 22 states have also undermined unions with so-called "right-to-work" legislation, which bans labor contracts that require all employees to join and pay union dues.