By Thomas Ferraro and Richard Cowan
WASHINGTON (Reuters) - A White House-backed bill to overhaul the U.S. immigration system got a boost on Tuesday when the non-partisan Congressional Budget Office concluded that the measure would cut federal budget deficits and boost the U.S. economy.
The CBO analysis came as the Senate fended off amendments by the bill's opponents that would have delayed for an unspecified amount of time provisions to legalize up to 11 million undocumented immigrants and allow them to gain citizenship within 13 years.
But House of Representatives Speaker John Boehner raised new doubts about the bill's prospect in his chamber, where many Republicans oppose the "pathway to citizenship" for illegal immigrants that President Barack Obama and his fellow Democrats have made a central feature of the sweeping measure.
The bill could pass the Democratic-led Senate by the end of this month.
According to the CBO, which assesses the cost and economic impact of legislation pending in Congress, the Senate bill would "boost economic output" and significantly reduce federal budget deficits over the next 20 years.
The White House embraced the CBO analysis, which was a rare bit of upbeat news after recent scandals over Internal Revenue Service handling of conservative groups' requests for tax-exempt status and disclosures of widespread government surveillance of telephone and Internet records.
"The Congressional Budget Office ... made clear that passage of the immigration bill would not only reduce the deficit, it would increase economic growth for years to come," White House Press Secretary Jay Carney said in a statement.
One outspoken critic of the Senate immigration bill, Republican Senator Jeff Sessions of Alabama, attacked the CBO findings, however, saying they failed to take into account longer-term costs related to the 11 million becoming legal residents and eventually qualifying for "Medicaid, food stamps and cash welfare."
Boehner made a surprise announcement on Tuesday when he told reporters he would only allow consideration of immigration bills backed by most of the 234 Republicans in the 435-member chamber.
"I don't see any way of bringing an immigration bill to the floor that doesn't have a majority support of Republicans," Boehner said after a closed-door meeting with his caucus.
Previously, Boehner had only said he would await Senate passage of a bill before deciding what course the House would take on an issue at the top of Obama's legislative agenda this year.
Many Democrats had hoped Boehner would advance a bill like the Senate's - one containing the pathway to citizenship - and that it could pass the House with the combined backing of most of the 201 House Democrats and some Republicans.
But the House Judiciary Committee worked on Tuesday not on pathways to citizenship for illegal immigrants but on a Republican proposal to clamp down on them.
It would do so by allowing state and local law enforcement officers to get involved in immigration enforcement, an activity now conducted by federal agents. It would also let states and localities enact and enforce their own immigration laws, as long as they were consistent with federal laws.
"We can't just be fixated on securing the (Southwestern) border," Judiciary Committee Chairman Bob Goodlatte said. He added that the Republican-backed bill would strengthen federal enforcement of immigration laws while ensuring "that where the federal government fails to act, states can pick up the slack."
Representative John Conyers, the senior Democrat on the committee, called the bill "extreme and heinous." He likened it to an Arizona state law he said had resulted in "widespread racial profiling and unconstitutional arrests."
Some Democrats said they were hopeful Boehner would back off his new requirement that any immigration bill be supported by a majority of House Republicans, just as he did in the past year on such issues as tax hikes on the wealthy, the U.S. debt limit, disaster relief and renewal of a landmark bill to curb domestic violence against women.
"Boehner is trying to maximize his leverage so he can get a bill that is as conservative as possible," one Democratic aide said.
SPLIT ON BORDER SECURITY
In the Senate, a split over how to strengthen border security has slowed action on the measure sponsored by a bipartisan "Gang of Eight."
Many Senate Republicans do not believe the bill's provisions to tighten security along the border with Mexico go far enough.
Senator John Hoeven of North Dakota said he and some fellow Republicans were making progress on a compromise amendment that could be unveiled as early as Wednesday to deal with border security.
Boehner echoed complaints by many Republicans about the Senate bill, saying he believed the measure "is weak on border security."
Once the Senate passes its bipartisan bill, there may be pressure on Boehner to bring it or a similar measure up for a vote in his chamber, even if most House Republicans oppose it.
"The political winds will be much different after the Senate passes its bill," the Democratic aide said, especially if there is an overwhelming bipartisan tally.
The Republican Party urged its members to embrace comprehensive immigration reform after last year's election, which saw 71 percent of Hispanics, members of the fast-growing voting bloc, support Obama's re-election.
(Additional reporting by David Lawder and Rachelle Younglai; Editing by Peter Cooney)