* Senators confident of passage next week
* Further amendments still possible
* Faces challenge in Republican-led House
By Richard Cowan and Thomas Ferraro
WASHINGTON, June 21 A landmark immigration bill appears headed toward passage next week in the U.S. Senate, where a test vote is set for Monday on a border-security deal designed to bolster Republican support.
The Democratic-led Senate is expected to pass the White House-backed bill and send it to the Republican-led House of Representatives, where it faces more resistance, especially over a provision that would provide a pathway to citizenship for up to 11 million illegal immigrants living in the United States.
Clearly confident of the outcome, Senate Majority Leader Harry Reid said on Friday, "Next week we're going to add immigration as another example on how we get things done" in the Senate with bipartisan collaboration.
Earlier this year, the Senate passed major bills on farm policy and stopping violence against women with bipartisan votes. These were rare bright spots after years in which Congress has been hamstrung by the inability of Democrats and Republicans to work together.
Reid scheduled Monday's vote after negotiators finished writing the border-security deal into the form of an amendment.
That amendment would double the number of federal agents on the U.S.-Mexican border to about 40,000 and provide more high-tech surveillance equipment, including manned and unmanned aerial vehicles.
Monday's vote, if successful, would clear procedural roadblocks that opponents otherwise could use to delay passage of both the amendment and the overall bill.
Reid hailed the accord, saying it "would put to rest any remaining critical concerns about border security," which had been a major stumbling block.
Earlier this week, House Speaker John Boehner raised worries about the fate of the immigration bill when he said he will not bring any measure to the floor of his chamber unless it has the support of most of his fellow Republicans.
The Senate will need 60 votes to move the border security amendment to passage. That amendment is seen as the last major step toward building a solid majority in support of a bill that also would update the U.S. visa system and achieve the broadest immigration reforms since 1986.
The border amendment, written mainly by Republican Senators John Hoeven of North Dakota and Bob Corker of Tennessee, was packed with a number of other changes to the bill.
They ranged from dealing with benefit eligibility for newly legalized immigrants to verification that employers do not hire unlawful workers.
Significantly, Republican Senator Orrin Hatch of Utah announced his support for the Hoeven-Corker measure after two of his amendments were tucked into it.
One would guard against those ineligible to work in the United States from drawing Social Security benefits while the other would prohibit welfare funds to any immigrant until he or she becomes a U.S. citizen.
"I've been clear that for any immigration reform legislation to be successful it needs to be fair to both American taxpayers and those wanting to become U.S. citizens," Hatch said in a statement.
SENATE BATTLE WINDING DOWN
Democratic and Republican aides said the Senate battle over the immigration bill is essentially over since the Hoeven-Corker amendment is almost certain to be approved.
Up to 70 of the Senate's 100 members are expected to vote for the overall bill, including all 52 Democrats, both independents and as many as 16 of 46 Republicans, aides for both parties said.
Once the border security amendment is dealt with, the Senate still could debate a few other proposals for changing the bill.
Democratic Senator Richard Blumenthal of Connecticut is teaming up with Republican Senator Lisa Murkowski of Alaska to try to expand the number of children of illegal immigrants who would be eligible for quicker citizenship under the bill.
Currently, the bill provides a five-year path to citizenship for such children, as opposed to 13 years for other illegal immigrants, but only if they are old enough to attend college or serve in the U.S. military.
Blumenthal wants to include younger children who meet other requirements of the bill, but he acknowledged it will be difficult.
Republican Senator Rob Portman of Ohio is pushing for another amendment to further strengthen an "E-Verify" program designed to help businesses hire only legally documented workers.
Portman wants to insert new protections for businesses that try to comply with the program and to beef up the security measures that help identify job applicants.