U.S. Senate heads for crucial immigration vote

By Donna Smith

WASHINGTON, June 28 (Reuters) - The U.S. Senate heads for a make-or-break vote on Thursday on President George W. Bush's plan to overhaul immigration laws after Senate leaders battled to fend off efforts by opponents to derail the bill.

The ultimate fate of the bill remained in doubt as the Senate prepared to decide on Thursday whether to bring debate to a close and move toward a final vote on the controversial legislation that would legalize millions of unlawful immigrants.

Supporters need 60 votes in the 100-member Senate to push the bill toward a final vote and they expect Thursday's tally to be close.

The bill's backers on Wednesday were able to kill a number of amendments they said would have undermined the fragile compromise crafted during months of negotiations by a group of Democrats and Republicans and the White House.

But they were unable to block a key amendment that would change worker identification requirements, casting doubt on the final outcome of the bill.

Bush has sought an overhaul of U.S. immigration laws for years and this bill may be his last chance for a significant domestic legislative victory before leaving office when his second term ends in a year and a half.

But the president has encountered fierce opposition from many fellow Republicans who say it would do little to stem the flow of illegal immigration into the United States.

The bill ties tough border-security and workplace- enforcement measures to a plan to legalize an estimated 12 million illegal immigrants and create a temporary worker program sought by business groups.