Sessions Says Immigration Bill Is a Threat to U.S. Workers Senator Jeff Sessions, the Republican from Alabama who may be the most determined and energetic opponent of an immigration overhaul bill now before the Senate, said on Friday that the legislation is "dangerous" for American workers, and he vowed to offer amendments in coming weeks to "confront the fundamentals of the bill" and slow its progress. On a conference call with reporters, Mr. Sessions made it clear that he hopes to reprise the leading role he played in 2007, when he helped rally popular resistance that defeated a similarly sweeping immigration bill by President George W. Bush. The senator warned that the bill would bring "explosive growth" in immigration, providing work authorization and legal status to more than 30 million immigrants over the next 10 years. Mr. Sessions said it would also "drastically increase low-skill chain migration." He pointed to a fast-track, five-year path to citizenship in the legislation for more than 2 million young immigrants brought here without authorization as children, who call themselves Dreamers. Mr. Sessions said that after they gained permanent legal status, those immigrants would be able to bring any of their family members, adding as many as 2 million more immigrants in future years. He also warned about the future impact of new guest worker programs for farm laborers and other low-wage migrants. "This large flow of workers will impact working Americans significantly," Mr. Sessions said, adding that the immigrants would lower salaries and compete for jobs. These numbers give a real warning to the American people of what is about to occur. The bill introduced last month by a bipartisan group of eight senators provides a 13-year path to citizenship for most immigrants here illegally, tightens border security, clears backlogs in the immigration system, creates new guest worker programs and expands visas for high-skilled immigrants. Senator Patrick J. Leahy, Democrat of Vermont and chairman of the Judiciary Committee, has said the process of adding amendments would begin next week. "There are so many problems with this bill, it is hard to know where to start," Mr. Sessions said. He said he planned amendments to increase local and federal immigration enforcement, curb future immigration and tighten visa background checks. The senator, who was in Alabama for the Congressional recess, acknowledged that supporters of the bill appeared to have the initiative so far. But as its details emerge, he said, "I do feel there is a change in this momentum." A demographer on the conference call, Steven A. Camarota from the Center for Immigration Studies, a study group in Washington that advocates lower immigration, estimated the American economy would have to create 35 million new jobs over the next 10 years to absorb new Americans in the labor force and new immigrants under the bill. "The coming decade would have to be the biggest job bonanza in American history," Mr. Camarota said. The senators sponsoring the bill have predicted far lower numbers of new immigrants. They note that most parents and many other family members of young Dreamers, for example, are already in the United States, most of them illegally but some with legal papers.