For all the talk about the inevitability of immigration reform, significant differences remain between the White House and Congress over border security and a pathway to citizenship for illegal immigrants, either of which could easily derail immigration reform talks this week.

Senators in the so-called Gang of Eight are on the verge of unveiling a plan that would create a path to citizenship for those in the U.S. illegally, a guest-worker program and some way to measure border security.

Republicans have shown an increased willingness for a deal after getting drubbed among Hispanic voters in November's election. Still, a sizable schism remains on the issues that will determine whether this latest immigration push fizzles like the others in years past.

"I'm a little bit amused by the chatter," a senior GOP Senate aide told The Washington Examiner. "We're not there yet. I'm not saying it won't ever happen, but we haven't seen anything yet that would give us confidence that a measure will clear this chamber, let alone the House."

In particular, Republicans remain skeptical about the Obama administration's commitment to securing the border, pointing out the lack of any objective way to measure security.

Republicans say they would continue to oppose citizenship for the 11 million immigrants living in the U.S. illegally until the border is secure -- and they say the public is with them.

A CNN poll released Monday found 50 percent disapproved of the way President Obama is handling illegal immigration, compared with 44 percent who approved.

Unlike his push for new gun restrictions, Obama is using a hands-off approach on immigration reform, not wanting to deter what the White House views as good-faith negotiations between Republicans and Democrats in Congress.

The closest thing to a deal maker -- or breaker -- on immigration reform is Sen. Marco Rubio, R-Fla., the GOP's rising Hispanic star, who could give fellow conservatives political cover whether they make a deal or not.

"We want to get the policy right," said Rubio spokesman Alex Conant, adding that the possible 2016 presidential candidate "isn't concerned about Beltway pressure to hurry immigration reform."

Republicans have long maintained that any proposal that creates a pathway to citizenship for illegal immigrants is akin to amnesty for lawbreakers. Sen. Jeff Sessions, R-Ala., on Monday questioned how many people would be legalized, the age required for eligibility, how long such people would need to live in the country and whether they can bring other family members from abroad.

Democrats say the citizenship measures can't be so rigid that they would prevent any illegal immigrant from coming forward. And some liberals argue Republicans have more incentive to compromise in the wake of their 2012 election defeats.

But conservatives aren't so eager to give in.

"It's a dangerous game for Democrats to assume the politics of this only favor them," said Matt Schlapp, White House political director for former President George W. Bush, who watched as Bush's own immigration reforms died on Capitol Hill. "You need a reasonable compromise -- and that starts with border security."