WASHINGTON — Supporters of bipartisan immigration legislation smoothed the way Friday for probable Senate passage of their handiwork, overcoming last-minute disagreements at the bill’s controversial core and tacking on other items certain to build support.
A test vote was scheduled for Monday on the bill, which calls for a military-style surge to increase security at the US-Mexican border. At the same time it sets out a 13-year pathway to citizenship for millions of immigrants living in the United States unlawfully.
Senator Lisa Murkowski of Alaska became the 11th Republican to announce her support for the legislation in the Democratic-controlled Senate. More were expected to follow, possibly enough to produce 70 votes or more and easily overwhelm its critics.
As part of late negotiations, the bill makes clear that no immigrant can get credit for payroll taxes paid when they lacked legal status. Credits are used to determine the level of Social Security benefits workers are entitled to in retirement.
Senator Bernie Sanders, a Vermont independent, joined by several Democrats, secured a $1.5 billion temporary jobs program for low-income youth. The funds will come from a temporary $10 surcharge imposed on visa applications from companies hiring guest workers and international workers who receive green cards.
Two provisions designed to aid Alaska seafood processors were backed by the state’s senators, Murkowski and Democrat Mark Begich.
The first permits companies to hire foreign students visiting the United States on so-called J-1 visas. The effect is to overturn a recent ruling by the departments of State and Labor that banned the practice. The second declares Alaska fish processing as a ‘‘shortage occupation,’’ which would expedite the industry’s ability to recruit seasonal workers outside the United States through a new W visa program set up in the bill.
Some Democrats said a heavy show of support at the end of next week could alter the bill’s trajectory in the House, where majority Republicans strongly oppose citizenship for immigrants who came to the country illegally or overstayed their visa.
‘‘Hopefully as congressmen look how their senators voted, they will be influenced by it,’’ said Senator Chuck Schumer of New York, who has played a major role for Democrats on the issue.
The bill’s critics made no claim they could block it in the Senate, but said their position would be vindicated in the long run.
Republican Senator Jeff Sessions of Alabama said the measure’s claims of border security were no different than previous assurances.
‘‘Time and again, politicians have promised, promised, promised. But they never delivered, delivered, delivered. And that’s a fact,’’ he said.
With immigration at the top of President Obama’s domestic agenda, White House spokesman Jay Carney labeled the Senate deal a breakthrough.
The day’s developments marked a victory for the Senate’s so-called Gang of Eight, four Democrats and four Republicans who for months worked on the basic framework of immigration legislation. They then warded off unwanted changes in the Senate Judiciary Committee last month, and in recent days, negotiated significant alterations with a group of Republicans who were uncommitted but willing to swing behind the bill if it were changed.
The principal demand was for tougher border security, particularly after the Congressional Budget Office estimated the bill would fail to stop a future buildup in the population of illegal immigrants.
Republican Senators John Hoeven of North Dakota and Bob Corker of Tennessee, who had spent about a week negotiating with members of the Gang of Eight for changes, announced the deal Thursday. A day later, Corker said in the Senate the bill is a chance to deal with ‘‘the issues of security many of our citizens across the country care about, but at the same time allow 11 million people to come out of the shadows and work in the light and be a part of this great, great nation.’’
The result of the talks was a series of costly and detailed steps to guard against future illegal immigration across the 2,000-mile border with Mexico.