In a new effort to crack down on illegal immigrants, federal authorities are expected to announce tough rules this week that would require employers to fire workers who use false Social Security numbers.
Officials said the rules would be backed up by stepped-up raids on workplaces across the country that employ illegal immigrants.
After first proposing the rules last year, Department of Homeland Security officials said they held off finishing them to await the outcome of the debate in Congress over a sweeping immigration bill. That measure, which was supported by President Bush, died in the Senate in June.
Now administration officials are signaling that they intend to clamp down on employers of illegal immigrants even without a new immigration law to offer legal status to millions of illegal immigrants already in the work force.
The approach is expected to play well with conservatives who have long demanded that the administration do more to enforce existing immigration laws, but it could also lead to renewed pressure from businesses on Congress to provide legal status for an estimated 6 million unauthorized immigrant workers.
"We are tough and we are going to be even tougher," Russ Knocke, the spokesman for the Department of Homeland Security, said Tuesday. "There are not going to be any more excuses for employers, and there will be serious consequences for those that choose to blatantly disregard the law."
Experts said the new rules represented a major tightening of the immigration enforcement system, in which employers for decades have paid little attention to notices, known as no-match letters, from the Social Security Administration advising that workers' names and numbers did not match the agency's records.
Illegal workers often provide employers with false Social Security numbers to qualify for a job.
Employers, especially in agriculture and low-wage industries, said they were deeply worried about the new rules, which could force them to lay off thousands of immigrant workers. More than 70 percent of farm workers in the fields of the United States are illegal immigrants, according to estimates by growers' associations.
"Across the employer community people are scared, confused, holding their breath," said Craig Regelbrugge, co-chairman of the Agriculture Coalition for Immigration Reform, a trade organization. "Given what we know about the demographics of our labor force, since we are approaching peak season, people are particularly on edge."
The expected regulations would give employers a fixed period, perhaps up to 90 days, to resolve any discrepancies between identity information provided by their workers and the records of the Social Security Administration. If workers' documents cannot be verified, employers would be required to fire them or risk up to $10,000 in fines for knowingly hiring illegal immigrants.
Immigrant rights groups and labor unions, including the AFL-CIO, predicted the rules would unleash discrimination against Hispanic workers. They said they were preparing legal challenges to try to stop them from taking effect.
(The new rules codify an uneasy partnership between the Department of Homeland Security and the Social Security Administration, which collects identity information from W-2 tax forms of about 250 million workers each year.