MADISON, Wisconsin (Reuters) - The Wisconsin state Assembly on Tuesday opened debate on a Republican proposal to curb the power of public sector unions that has sparked mass demonstrations and a tense stand-off with Democrats. Hundreds of protesters choked the Capitol halls again on Tuesday chanting "It's about rights, it's not about money," while others banged plastic pails outside in opposition. The proposal would strip most collective bargaining rights from many state workers. Wisconsin Senate Democrats, who fled the state last Thursday to deny a quorum for voting on the budget proposal, stayed outside the state again on Tuesday. But Republicans pushed ahead in the Assembly where they have a strong enough majority to pass the proposal. Democrats vowed to flood the bill with dozens of amendments in a bid to derail it. "I cannot express in strong enough terms that our goal is not to delay this bill. Our goal is to stop this bill, end the impasse and start over," state Assembly Democratic leader Peter Barca said Tuesday. Barca presented 15 amendments at the opening of debate and said dozens more were ready to be introduced, moves Republican Assembly Speaker Jeff Fitzgerald called "delaying tactics." Republican Gov. Scott Walker has said state employee layoff notices could be issued as soon as next week if the impasse continues. Wisconsin has become the flashpoint for a struggle over efforts to roll back pay, benefits and bargaining rights of government workers. If the majority Republicans prevail, several other states could be buoyed in efforts to take on the powerful public unions. Walker, who plans a televised address on Tuesday evening, has said the state is broke and there is no room to compromise on the proposal. State and local governments are struggling to balance budgets after the recession decimated their finances. Other states like Texas, Arizona and Ohio are relying mainly on cuts in spending, while Minnesota and Illinois are raising taxes. Extra security was in place to handle massive crowds again on Tuesday. Security officers searched backpacks of visitors and large areas of the Capitol building in Madison were cordoned off with yellow crime scene tape. The changes sought by Walker in Wisconsin would make state workers contribute more to health insurance and pensions, end government collection of union dues, let workers opt out of unions and require unions to hold recertification votes every year. Collective bargaining would be allowed only on wage increases up to the rate of inflation. Walker wants the bill passed by Friday as part of a plan to push principal payments on general obligation bonds into future years to save $165 million. Under that plan, the bill must be passed by Friday to allow time to sell the debt.