By Richard Cowan and Caren Bohan
WASHINGTON (Reuters) - A small group of Republican senators worked Monday on a possible border security compromise that would make a sweeping immigration bill more acceptable to some otherwise reluctant conservatives.
The proposal is aimed at a satisfying calls by Republicans for further steps to secure the U.S.-Mexico border as part of the legislation currently being debated in the U.S. Senate that would grant legal status to millions of undocumented immigrants already in the United States.
It could include provisions for deploying high-tech surveillance equipment and other specifics, according to congressional sources and people close to the talks.
The sources said the amendment would give Congress a bigger role in overseeing border security steps to be taken by the Department of Homeland Security.
Senators Marco Rubio of Florida, Bob Corker of Tennessee and John Hoeven of North Dakota were said to be working on an amendment that could be offered as early as this week.
"There's a number of conversations that are under way," Corker told reporters. "It continues to be slightly fluid."
He said the senators are seeking a proposal that "acknowledges the Democratic sensibilities but also causes border security to be addressed properly from" the Republican side.
The proposal might not go as far as some conservative Republicans would like in toughening up "triggers" in the bill that would make the path to citizenship for undocumented workers contingent on meeting certain goals for securing the U.S.-Mexico border.
Rubio, one of the eight authors of the Senate immigration bill, has taken the lead in trying to court conservative support for the bill. He repeatedly has said he wants to see stronger language in it on border security. On Sunday, he told the ABC News program "This Week" that he thought the immigration bill was 95 percent or 96 percent ready but needed some changes.
The amendment under discussion would spell out amounts of money that must be spent to provide security enhancements, such as unmanned aerial drones to watch for illegal border crossings.
In providing greater specificity on the instructions to DHS for securing the border, the proposal resembles one put forth by Kentucky Senator Rand Paul, a conservative who has said he might be open to voting for the immigration bill if some changes were made.
But unlike Paul's proposal, the measure under consideration would not require Congress to take annual votes reviewing progress on securing the border. Under Paul's plan, green cards or permanent residence for undocumented immigrants could be in jeopardy if Congress does not certify that the border is secure.
"What I like about it is ... if they (DHS and Congress) don't meet the marks, they're the ones held accountable, not the lives of 11 million people," said an immigration advocate familiar with the proposal under consideration.
Texas Senator John Cornyn has offered a controversial amendment that would delay permanent legal status or "green cards" for undocumented immigrants if the government fails to meet goals, such as achieving full surveillance of the U.S.-Mexico border and stopping 90 percent of illegal crossings.
Democrats view Cornyn's plan as a "poison pill" meant to kill the legislation by shattering its bipartisan support. Republican Senator John McCain of Arizona also has sharply criticized it.
But Rubio has been more supportive. In an interview with Fox News this week, Rubio called the Cornyn proposal an "excellent place to start."
"I think whether Rubio would vote for the Cornyn amendment is going to be a big question," said Lanae Erickson Hatalsky, an immigration expert at the Third Way think tank.
Border security has loomed as a difficult issue for the bipartisan "Gang of Eight" senators who wrote the immigration bill.
The senators have struggled with the issue of how closely to tie the promise of citizenship for illegal immigrants to the goal of fortifying the border.
Republicans argue that tough border security "triggers" are needed to ensure that the granting of legal status to undocumented immigrants is not followed by a new wave of illegal immigration.
But Democrats say the 13-year path to citizenship in the bill is already a lengthy one and should not be subject to further uncertainties.
Though Democrats are expected to provide a large majority of the votes needed to pass the immigration bill in the Senate, several Republican votes will be needed to meet the 60-vote threshold required for approval.
If the bill passes the Senate, it will face a challenge in the Republican-dominated House, where many conservatives oppose to granting legal status to undocumented immigrants.
Asked last week how the differences over border security could be bridged, McCain told reporters that technology - such as drones and other surveillance equipment - was "one of the ways we get there" with a compromise amendment that further improves border control.
(Reporting by Caren Bohan; Editing by Fred Barbash and Bill Trott)