WASHINGTON, May 1 (Xinhua) -- Organizers predict unprecedented participation in Monday's rallies against a proposed crackdown on illegal immigration, with millions expected to boycott jobs, schools and businesses as a way to show the economic power of immigrants.

    The demonstrations, dubbed "A Day Without Immigrants," follow previous rallies that drew crowds estimated at hundreds of thousands in Los Angeles, California, and Dallas, Texas.

    Other cities, including Atlanta, Georgia; Milwaukee, Wisconsin;and Phoenix, Arizona, saw tens of thousands of people turn out forsuch protests.

    But Monday's events will be unprecedented in their scope, said Nativo Lopez, president of the Mexican-American Political Association, one of the organizers of the rallies.

    "We're going to see something that's never occurred in the history of this United States -- a day in which immigrants withhold their labor, withhold their consuming power -- they don'tgo to school, they don't go shopping, they don't go selling," Lopez said.

    About 7.2 million illegal immigrants hold jobs in the United States, making up 4.9 percent of the overall labor force, according to a recent study by the Pew Hispanic Center.

    Other estimates put the number of illegal immigrants in the United States at more than 11 million.

    The protests began in March against a congressional bill that would make felons of illegal immigrants and wall off over a third of the U.S.-Mexican border.

    The bill passed the House of Representatives in December 2005 but has stalled in the Senate.

    The immigration debate has split Republicans as midterm elections approach.

    U.S. President George W. Bush, taking great pains to woo Latino voters to his party, has called for a guest-worker program and a way to legalize the status of people in the United States illegally.

    In April, a compromise Senate bill backed by Senators Chuck Hagel of Nebraska and Mel Martinez of Florida had attempted to make the legalization process tougher for illegal immigrants who have been in the country less than five years.

    But the bill stalled when Senate Minority Leader Harry Reid objected to Majority Leader Bill Frist's decision to let Republican senators offer amendments to the measure. Enditem