BUENOS AIRES, Argentina (AP) _ Leaders of some of Argentina's most powerful unions marched Wednesday, calling for the repeal of a labor reform bill at the center of a Senate bribery scandal.

The march through downtown Buenos Aires drew 5,000 union members, state workers and unemployed people and ended with a demonstration in front of the presidential palace, the Casa Rosada.

Hugo Moyano, head of the unofficial labor movement, warned in a speech that the unions were prepared to do whatever it takes to have the labor law and salary cuts for public workers struck down.

``If we have to strike, we will strike. If we have to fill the squares with protesters, we will fill them.'' Moyano told a cheering crowd.

The labor law was passed in May by Congress, the centerpiece of the economic strategy of the nine-month old administration of President Fernando De la Rua. The measure was aimed at kick-starting the sluggish Argentine economy out of its 16-month-old recession.

The law seeks to increase labor flexibility and attract investment by decentralizing collective bargaining and extending the trial period of newly hired workers from 30 to 90 days.

The law has become the focus of a Senate bribery scandal, in which members of the governing Alliance administration are said to have paid opposition Peronist senators to vote in favor of the bill.

Protesters at the march made it clear that they believed the allegations fully. Many carried placards daubed with colorful images of Labor Minister Alberto Flamarique.

The unions also called on the government to reverse its decision to cut salaries for state workers by up to 15 percent. The reductions in salary were passed as part of an austerity plan intended to meet guidelines of the International Monetary Fund through tax hikes and spending cuts.