President Barack Obama pushed Congress on Tuesday to overhaul the U.S. immigration system but disagreement with Republicans over securing the border with Mexico has already begun to sour bipartisan efforts.
"We need Congress to act on a comprehensive approach that finally deals with the 11 million undocumented immigrants," Obama said at a high school in Las Vegas.
After years on the back burner, immigration reform has suddenly looked possible as Republicans, chastened by Latino voters who rejected them in the November election, look more kindly on an immigration overhaul.
Obama spoke a day after a group of influential Senate Democrats and Republicans laid out a broad plan of their own that is similar to White House immigration proposals.
But differences quickly emerged between what Obama would like and the proposals by the bipartisan "Gang of Eight" senators.
While the senators' plan insists on first toughening border security before allowing illegal immigrants to take steps to gain citizenship, the Obama plan does not.
That difference was enough to raise concerns among Republican lawmakers who are trying to frame a package that can pass the Republican-led House of Representatives. A Hispanic Republican, Senator Marco Rubio, warned Obama not to ignore his party's concerns about border security.
"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."
Under the Obama proposal, undocumented workers would be required to register, undergo national security and criminal background checks, pay fees and penalties, learn English and go to the back of the immigration line behind those who are applying to enter the country legally.
"We all agree these men and women should have to earn their way to citizenship. But for comprehensive immigration reform to work, it must be clear from the outset that there is a pathway to citizenship," Obama said.
However, Republicans will likely oppose any immigration plan that doesn't put border security first.
"This provision is key to ensuring that border security is achieved, and is also necessary to ensure that a reform package can actually move through Congress," said newly elected Senator Jeff Flake of the border state of Arizona.
Another point of contention is expected to be whether same-sex couples are granted the same benefits as heterosexual couples under immigration reform - something the White House says Obama will insist upon but which the Senate group did not deal with.
Obama's speech in Nevada a little more than a week after his second inauguration reflects the growing clout of Hispanic voters, as does Republican willingness to move on the issue.
The Democratic president said that if Congress is unable to act in a timely fashion, he will propose immigration legislation of his own and "insist that they vote on it right away."
Immigration reform could give Obama a landmark second-term legislative achievement, but the White House is mindful that success on such a divisive issue will require a delicate balancing act.
(additional reporting by Jeff Mason, Roberta Rampton and Steve Holland, Editing by Alistair Bell and Doina Chiacu)