Unauthorized immigrants may have to pay $2,000 as part of a bipartisan U.S. immigration reform plan, a person familiar with the talks told The New York Times.
The fee, whose amount was not finalized but which would have to be paid before an immigrant could earn legal status, would include $500 when the person applies for a temporary work permit and $1,500 or so that the person would have 10 years to pay, before they apply for a green card, the person said.
A Senate aide described the $2,000 figure to the Times as "significant but not impossible, punitive but not unreasonable."
Democrats and immigration advocates had earlier pushed for a lower amount.
The fees, reported Monday, came a day after Sen. Marco Rubio, R-Fla., dismissed colleagues' fears the immigration overhaul that awards citizenship to people in the United States illegally would amount to amnesty.
"It's not amnesty because you pay serious consequences for having violated the law," the first-term senator and possible 2016 presidential contender told NBC's "Meet the Press."
The measure would boost the number of taxpaying Americans and be a "net positive for the country economically, now and in the future," Rubio told "Fox News Sunday" in one of seven Sunday talk show interviews he did on the five major networks, plus the Spanish-language Telemundo and Univision networks.
The measure -- expected to be unveiled by Rubio and seven other senators of both parties as early as Tuesday -- calls for unauthorized immigrants who arrived in the United States on or before Dec. 31, 2011, to be allowed almost immediately to apply for temporary legal status that would let them live and work in the country.
At the same time, the Department of Homeland Security would be required to monitor the nation's entire southwest border with Mexico -- and catch 90 percent of people trying to cross the border illegally, said Rubio, a member of the so-called Gang of Eight senators.
"We are going to get the toughest enforcement measures in the history of this country," he told ABC's "This Week."
In addition, the senators' plan also requires business owners to use the federal government's free, Web-based E-Verify system that checks new employees' immigration status.
Washington would also have to identify each time a foreigner enters and exits the country, USA Today reported.
If those benchmarks are reached, and after 10 years pass, unauthorized immigrants could apply for a green card, which grants permanent legal status. If approved, they could apply for U.S. citizenship three years later.
"I'm very optimistic about it," Rubio said on the CBS News program "Face the Nation" in a reversal of the caution he expressed about the measure several weeks ago.
The bill is expected to be examined by the Senate Judiciary Committee Wednesday.
Rubio said lawmakers would have weeks to study the bill, but he also told CNN's "State of the Union" he expected unspecified lawmakers would introduce amendments "designed as poison pills" to doom the measure.
"I'll oppose those if I know that's what they're for," he said.
Sen. Jeff Sessions, R-Ala., who appeared on ABC's "This Week" after Rubio, said he was "not convinced" by his colleague's pitch.
"I know Senator Rubio's heart is exactly right," he told the program. "And I really respect the work of the Gang of Eight. But they have produced legislation, it appears ... that will give amnesty now, legalize everyone that's here effectively today, and then there's a promise of enforcement in the future.
"Even if you pass laws today that appear to be effective, it doesn't mean they're going to be enforced," Sessions said.
Rubio said newly legalized immigrants wouldn't receive federal benefits during the 13 or so years it would take them to qualify for full legal citizenship.
"This is an important point. No federal benefits, no food stamps, no welfare, no Obamacare," he said on Fox.
"They have to prove they're gainfully employed," he said. "They have to be able to support themselves, so they'll never become a public charge."
Rubio is a son of Cuban immigrants. Cuban immigrants, through the Cuban Refugee Adjustment Act, can become permanent U.S. residents after a year. Being a public charge doesn't make a Cuban ineligible to become a permanent resident.