Federal authorities would be required to establish vast new border fences and surveillance as part of a bipartisan Senate plan aimed at allowing the nation’s 11 million illegal immigrants to earn permanent residency and, potentially, citizenship, aides familiar with the proposal said Wednesday.

The provisions would call on the Department of Homeland Security (DHS) to increase surveillance to cover 100 percent of the Southwestern border and to apprehend 90 percent of the people who attempt to enter the United States illegally, said the aides, who spoke on condition of anonymity to disclose private negotiations.

An eight-member Senate group is nearing agreement on a comprehensive proposal that would represent the most sweeping overhaul of the nation’s immigration laws in nearly three decades. Aides said the legislation will be unveiled ahead of a hearing on the bill scheduled Wednesday in the Senate Judiciary Committee.

Homeland Security Secretary Janet Napolitano, who is expected to testify, recently expressed skepticism about the idea of using new border-control metrics as a “trigger” that would make or break a path to citizenship for undocumented migrants.

Advocates also have voiced concerns about tying border security to the path to citizenship, saying they feared that disputes over the effectiveness of the new measures could delay the process for undocumented residents. President Obama has said a comprehensive immigration bill must offer a “clear path” to citizenship.

Democrats emphasized that the new border-control metrics represent “goals” but are not intended as specific “triggers” that would potentially delay the path to citizenship.

“The legislation spells out goals,” one Democratic aide said. “These are resource-based measures, not outcome-based.”

The Obama administration has said the border is already more secure than it has been in decades. But the Government Accountability Office found that the Border Patrol had only 44 percent of the Southwestern border under “operational control” in 2010.

Nestor Rodriguez, a professor at the University of Texas who has studied the Southwestern border, said that although it is possible to surveil the entire border, it might not be necessary, especially considering the enormous financial investment required.

The four Republicans in the working group, including Sen. Marco Rubio (R-Fla.), pushed hard for beefed-up security measures, which are viewed as critical to garnering GOP support in the Senate and House for a comprehensive reform bill.

Asked if the provisions were strong enough to convince his GOP colleagues to support the bill, Sen. John McCain (R-Ariz.), a member of the working group, said Wednesday: “Damned if I know.”

Rubio has been cautious in his public statements about the legislation. He was expected to brief the GOP caucus at its Wednesday luncheon, but did not because senators were focused on an emerging bipartisan agreement on background checks for private gun sales, aides said.

GOP aides said the border-control measures were meant to assure immigration skeptics that significant new security provisions would be in place before illegal immigrants are rewarded with green cards, which signify permanent-resident status, or citizenship.

Under the terms of the proposal, DHS would submit a plan to reach the new milestones within nine months of the immigration legislation becoming law. The bill authorizes $3 billion to help the agency deploy new surveillance technology, including aerial drones for treacherous border regions, and build new fencing.

Another $4 billion would go toward expanding a workplace screening system known as E-Verify and setting up a border entry-exit tracking system to identify foreigners who have overstayed their visas, Senate aides said.

If DHS is unable to meet the benchmarks within five years, a border commission composed of governors and attorneys general in Southwestern states would receive federal funds to pursue additional measures for five more years.

“The takeaway here is that this will easily be the toughest border-enforcement system this country has ever had,” a Republican aide said.

Aaron C. Davis contributed to this report.

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