The deal was developed by Republican Sens. Bob Corker of Tennessee and John Hoeven of North Dakota, in consultation with Schumer, McCain and other members of the so-called Gang of Eight senators who wrote the immigration bill. It prevents immigrants now here illegally from attaining permanent resident status until a series of steps have been taken to secure the border.
These include doubling the Border Patrol with 20,000 new agents, 18 new unmanned surveillance drones, 350 miles of new fencing to add to the 350 miles already built, and an array of fixed and mobile devices to maintain vigilance, including high-tech tools such as infrared ground sensors and airborne radar.
The new provisions would be put in place over a decade, in line with the 10-year path to a permanent resident green card that the bill sets out for immigrants here illegally. During that time, the immigrants could live and work legally in a provisional status.
Vice President Joe Biden told a predominantly Latino crowd of 1,100 gathered in Las Vegas for the national conference for the League of United Latin American Citizens that now is the time for a "fair, and firm and unfettered path for 11 million people" to become U.S. citizens.
(Read More: CBO: Senate Immigration Plan Would Boost Economy)
"The question you should ask is, `What will immigration reform do for America?"' Biden said Thursday. "The answer is clear and resounding: It can and will do great things for America."
Hoeven said the 10-year cost included $25 billion for the additional Border Patrol agents, $3 billion for fencing and $3.2 billion for other measures.
It's "border security on steroids," said Corker, who along with Hoeven had been uncommitted on the immigration bill. Both are now prepared to support it, assuming their amendment is adopted, as is expected to happen early next week. Sens. Dean Heller, R-Nev., and Mark Kirk, R-Ill., also announced their support Thursday.
Corker and Hoeven had said they expected the legislation to be formally unveiled in the Senate late Thursday, but for unexplained reasons that did not happen. Senate Majority Leader Harry Reid, D-Nev., adjourned the Senate around 10:30 p.m., saying the amendment was nearly ready and the Senate could move forward with it Friday.
The deal on border security came together quickly earlier this week after talks had bogged down over Republicans' insistence that green cards be made conditional on catching or turning back 90 percent of would-be border crossers. Schumer, other Democrats and Obama himself rejected this trigger, which they feared could delay the path to citizenship for years.
The breakthrough came when the Congressional Budget Office released a report Tuesday finding that the bill would cut billions of dollars from the deficit.
Sen. Lindsey Graham, R-S.C., an author of the bill who helped run interference between Corker and Hoeven and Democrats in the group, said that with the CBO finding in hand, he sat down with Schumer and Corker and said, "OK, let's go big."
The idea immediately appealed to the left and the right.
For Republicans, it provided concrete assurances that the bill would achieve a secure border. For Democrats, it offered goals that, if dramatic, were achievable and measurable.
Still, not everyone was won over.
Shortly before Corker and Hoeven went to the Senate floor to announce their agreement Thursday afternoon, five leading Republican opponents of the bill held a news conference to denounce the deal as little more than an empty promise.
"In short I think this amendment is designed to pass the bill but not to fix the bill," Sen. David Vitter, R-La., said.
About 10 Republicans have indicated they will vote for the bill, far more than enough to ensure it will have the 60 votes required to overcome any attempted filibuster by last-ditch opponents. Democrats control 54 seats, and party aides have said they do not expect any defections.
In addition to the border security components and eventual citizenship for the 11 million people now here illegally, the immigration bill would create new work visa programs and expand existing ones to allow tens of thousands of workers into the country to work in high- and low-skilled jobs.
Employers would have to verify their workers' legal status.
—By The Associated Press.