WASHINGTON, May 24 (Xinhua) -- The U.S. Senate has passed an amendment to cut in half the number of guest workers who would be allowed into the United States under an immigration reform plan backed by the White House, CNN reported on Thursday.

    The amendment, passed on a 74-24 vote on Wednesday night, was the first major change to a "grand bargain" unveiled last week and sent to the Senate floor for debate on Monday.

    Senators voted to reduce the number of guest workers that would be allowed into the country from 400,000 to 200,000.

    Democratic Senator Jeff Bingaman of New Mexico, the leading advocate of the amendment, said 200,000 guest workers would be "plenty."

    But Republican Senator Arlen Specter of Pennsylvania said the 400,000 figure was chosen as a result of "very careful analysis and consideration."

    The immigration bill is the result of a deal struck after nearly three months of bipartisan talks and endorsed by the White House last week.

    It plans to offer an estimated 12 million illegal immigrants now in the country a path to citizenship, boosting border controls and establishing a guest-worker program that would grant foreign workers a two-year residency.

    Conservative critics have blasted it as "amnesty" for illegal immigrants, while liberals have raised concerns that the guest-worker program would create a permanent underclass.

    Bingaman's amendment was the second of two Democratic proposals aimed at drastically altering the bipartisan "grand compromise" on immigration reform.

    The first, which would have eliminated the guest worker program as a whole, was voted down on Tuesday.