U.S. Senate Majority Leader Harry Reid (D-NV) speaks to the media about the immigration reform bill on Capitol Hill in Washington June 18. (YURI GRIPAS/REUTERS)

The immigration bill under consideration in the Senate would reduce federal deficits by nearly $200 billion over the next decade, and continue generating savings in the years beyond, even after millions of new citizens became eligible for health-care and welfare benefits, congressional budget analysts said Tuesday.

The long-awaited report by the nonpartisan Congressional Budget Office marked a major victory for the bipartisan “Gang of Eight” senators who have spent months negotiating the details of the measure. Although some conservatives say the bill would cost the nation billions of dollars, CBO analysts concluded the opposite, undercutting a potentially powerful argument against the measure.

“This report is a huge momentum boost for immigration reform,” said Sen. Charles E. Schumer (N.Y.), the lead Democratic negotiator. “This debunks the idea that immigration reform is anything other than a boon to our economy and robs the bill’s opponents of one of their last remaining arguments.”

The White House welcomed the report, saying in a statement, “Today, we have more proof that bipartisan commonsense immigration reform will be good for economic growth and deficit reduction: this time, in the form of a nonpartisan Congressional Budget Office estimate.”

Republican reaction was mixed. Sen. Jeff Sessions (Ala.), an opponent, said the report made clear that he measure would lower overall wages and increase the unemployment rate for years.

“This is supposed to be good for the people we represent?” he said in a speech on the Senate floor. “And, of course, I would like to again ask our colleagues to think carefully about our duty here, who it is we represent in this body and what kind of responsibilities we have to decent, hard-working Americans who experts have told us have seen their wages decline every year virtually since 1999.”

The 63-page report concludes that the Senate’s immigration bill would increase the U.S. population by about 10.4 million people through 2023 and about 16.2 million by 2033.

In addition, about 8 million people currently living in the United States illegally would gain legal status under the legislation, the CBO said.

Those changes would boost spending on federal programs, including tax credits for low-income families, health-care benefits and law enforcement, the agency found. But those costs would be more than offset by an increase in tax revenue from a larger workforce, it said. In its second decade, when people currently living here illegally would become eligible for federal benefits, the legislation would reduce deficits by as much as $1 trillion, the CBO said.

The report comes at a critical moment in the months-long effort to overhaul the nation’s immigration laws. The Senate began voting Tuesday afternoon on amendments to a comprehensive proposal, which Senate Majority Leader Harry M. Reid (D-Nev.) has vowed to push to final passage by the Fourth of July recess.