A bipartisan group of US lawmakers is on the cusp of introducing the most sweeping immigration reform in a quarter century, in what could amount to a dramatic victory for President Barack Obama.
A Senate bill is now expected to be unveiled as early as Monday, Democrat Robert Menendez, one of eight senators tasked with thrashing out the deal, said at a major immigration reform rally Wednesday outside the US Capitol.
Several members of the so-called Gang of Eight -- four Democrats and four Republicans -- have said it would contain a long-term path to citizenship for most of the country's 11 million undocumented migrants.
The bill will include an expansion of quotas of foreign workers, as well as demand stringent -- and expensive -- new tightening of border security measures.
Immigration reform has been a key recent focus for Obama, while Republicans smarting from their 2012 election defeat are seeking to broaden their outreach to minorities, particularly the Hispanic community.
Some of the lawmakers negotiating since February, including Senator John McCain, had been hoping to introduce their measure as early as Thursday, but it is now likely in the coming week, sources said.
"We are very, very close," Republican Senator Lindsey Graham told AFP.
In a sign that a deal was imminent, Senate Judiciary Committee Chairman Patrick Leahy scheduled a hearing on the bill for April 17, heaping pressure on the negotiators to finalize the legislation.
A Senate aide said Leahy has promised to allow unlimited debate and amendments during committee consideration of the measure.
Alex Burgos, a spokesman for Senator Marco Rubio, said the Senate Republican Policy Committee has also agreed to host a public hearing after the bill is introduced.
"We believe that the more public scrutiny this legislation receives, the better it will become," he said.
Rubio -- a Cuban-American and potential 2016 presidential candidate who has emerged as a key voice on immigration -- has joined other Republicans in demanding a comprehensive internal debate on any legislation.
According to a person familiar with the plan, illegal immigrants would be barred from applying for permanent legal residency until authorities are monitoring 100 percent of the southern US border with Mexico and stopping 90 percent of the people crossing illegally in some areas.
Meeting that goal and other security requirements of the broader bill could take up to a decade, the source said.
"There will be tough but achievable hurdles that tie border security directly to the pathway to citizenship, and if these triggers are not part of the legislation, there won't be any deal," Burgos said.
As senators worked out the finishing touches, more than 10,000 people converged on the west side of the US Capitol demanding action.
"We know, as every American who is honest with themselves knows, that if you had fruit for breakfast this morning, it was probably picked in the hot sun by an immigrant worker with a bent back and a sunburn," Menendez told the crowd, peppering his speech with Spanish.
"These are people doing the jobs to build America, and it's time to give them the dignity that they deserve and the opportunity to earn their way to the American dream."
Another bipartisan immigration bill is meanwhile being crafted in the Republican-led House of Representatives, amid public sentiment that appears increasingly in favor of a comprehensive solution.
According to a March 21 survey, six out of 10 Americans support a path to citizenship for undocumented immigrants.
The last major immigration reform dates back to 1986 when, with Republican icon Ronald Reagan in the White House, some 3.5 million illegal immigrants were granted amnesty.
The United States currently deports about 400,000 people annually.
Employers and unions are carrying out parallel negotiations to expand and overhaul entry quotas for workers in all sectors.
"There is immigration reform that's going to be passed, but the devil's in the detail," said Maria Castro, a 19-year-old Arizona State University student and US-born citizen whose mother is an undocumented worker.