Hours before President Obama is set to deliver a major immigration speech, a key Republican senator blasted the president for reportedly opposing a requirement to shore up border security before legalizing up to 11 million illegal immigrants.
Sen. Marco Rubio, R-Fla., one of four Republican senators involved in a bipartisan effort to craft immigration reform legislation, warned the president Tuesday against taking such a position. It was the first sign since the senators unveiled their guidelines a day earlier of friction between the two efforts.
"I think that would be a terrible mistake," Rubio told Fox News. "We have a bipartisan group of senators that have agreed to that. For the president to try to move the goalposts on that specific requirement, as an example, does not bode well in terms of what his role's going to be in this or the outcome."
Rubio, a prominent conservative who is also Hispanic, is vital to the bipartisan effort on Capitol Hill. The senator, though, insisted that illegal immigrants not be allowed to obtain green cards -- let alone citizenship -- "until the enforcement stuff is in place."
"If that's not in the bill, I won't support it," he said.
Rubio was responding to reports that Obama, who is traveling to Las Vegas Tuesday to outline his immigration reform vision, does not want to make the legalization process contingent on increased border security.
Rather, the administration is looking at a smoother process. One administration aide said illegal immigrants would be required to pay back taxes and a fine, and move to the back of the line after would-be legal immigrants, in order to apply for legal status and eventually citizenship.
In Obama's earlier proposal, which he is expected to largely follow, he also says those applying for citizenship must learn English. After eight years, individuals would be allowed to become legal permanent residents and could eventually become citizens five years later.
The issue of immigration reform was put on the back burner during Obama's first term -- overtaken by debate over health care legislation and economic measures. But along with gun control, it is one of the top items on his second-term domestic agenda.
The eight U.S. senators got ahead of him Monday, unveiling a blueprint that calls for, among other things, a path to citizenship for the 11 million illegal immigrants already in the United States.
But White House Press Secretary Jay Carney said the president "welcomes" the proposal, saying it represents the "bipartisan support coalescing" behind certain principles of immigration reform.
"This is an important first step. ... We need to continue the movement," Carney said.
Despite the difference over the path to legal status, an Obama administration official told Fox News the senators' plan is on a trajectory that mirrors Obama's immigration plan in many ways, and that the White House is willing to let the group take the lead.
Sen. Chuck Schumer, D-N.Y., one of the eight senators, called the new proposal a "major breakthrough" and said he hopes to turn it into legislation by March -- with the goal of passing something out of the Senate "by late spring or summer."
Sen. John McCain, R-Ariz., standing beside him, claimed 2013 is the "best chance" lawmakers will have to tackle immigration for years.
Even so, the proposed pathway to citizenship for illegal immigrants drew immediate criticism from others on Capitol Hill.
"No one should be surprised that individuals who have supported amnesty in the past still support amnesty," Rep. Lamar Smith, R-Texas, said. "By granting amnesty, the Senate proposal actually compounds the problem by encouraging more illegal immigration."
The eight senators who unveiled the new principles are Democrats Schumer, Dick Durbin of Illinois, Robert Menendez of New Jersey and Michael Bennet of Colorado; and Republicans McCain, Lindsey Graham of South Carolina, Rubio of Florida and Jeff Flake of Arizona.
The Senate framework would also require those here illegally to pass background checks and pay fines and taxes in order to qualify for a "probationary legal status" that would allow them to live and work here -- but not qualify for federal benefits -- before being able to apply for permanent residency, a critical step toward citizenship. Once they are allowed to apply they would do so behind everyone else already waiting for a green card within the current immigration system.
Senators also want to reform the legal immigration system, including awarding green cards to immigrants who obtain advanced degrees in science, math, technology or engineering from an American university.
The principles released Monday are outlined on just over four pages, leaving plenty of details to fill in.
A Senate aide tells Fox News the group's principles say important security triggers must be met before a pathway for citizenship is created for illegal immigrants. Even then, the principles explicitly state that illegal immigrants must go to the back of the line behind would-be legal immigrants, and they will not be eligible for federal benefits while in the temporary legal status.
The aide told Fox News that although many of the details of the bill still need to be worked out, those involved are encouraged by their progress and the support of senior senators. Members of the group on Sunday said they are seeking to craft a one-step, all-encompassing bill based on the shared principles.
Most of the recommendations Obama will make Tuesday are not new. He outlined an immigration blueprint in May 2011 but exerted little political capital to get it passed by Congress, to the disappointment of many Hispanics.
Administration officials said the president would bolster that 2011 blueprint with fresh details. His original plan centered on four key areas: a pathway to citizenship for the 11 million illegal immigrants in the U.S., improved border security, an overhaul of the legal immigration system and making it easier for businesses to verify the legal status of workers.
Administration officials said they were encouraged to see the Senate backing the same broad principles. In part because of the fast action on Capitol Hill, Obama does not plan to send lawmakers formal immigration legislation.
However, officials said the White House does have legislation drafted and could fall back on it should the Senate process stall.
The Associated Press contributed to this report.