Rubio is one of eight senators who, on Monday, unveiled a bipartisan framework for passing immigration reform. The framework includes creating a pathway to citizenship, increasing the number of visas for high-skilled immigrants, implementing an employer verification system and setting up a new guest-worker program.

"Well look, I love and respect Marco. I think he's just amazingly naive on this issue. This is the same old formula that was dealt with before, including when it passed in 1986, and that is promises of enforcement and immediate amnesty," Vitter said in an interview on the Laura Ingraham radio show released Wednesday. 

"And of course the promises of enforcement never materialize, the amnesty happens immediately — the millisecond the bill is signed into the law. The same is true here. No, they won't be citizens immediately. They will be legal, they will have a full right to stay in this country forever legally. And then the only question is how long does that take? It's gonna happen. I don't know if it's a year, five years longer but citizenship is guaranteed at that point as a practical matter."

The framework also requires strengthening border enforcement before the new pathway to citizenship is offered. Vitter expressed skepticism about that provision.

"Look, as soon as you give these people a legal status, to say that you're gonna reverse that is ridiculous," Vitter said. "It'll never happen. As soon as you give them a legal status, they are here forever, and probably they're citizens soon thereafter."

Instead of the senators' immigration framework, Vitter wants to see a "piecemeal" approach, he said.

"First of all, I think we need to focus on that this is comprehensive reform. To me that is a really negative buzzword," Vitter said. "As a conservative I'm usually against anything 'comprehensive' because that's big government with all sorts of unintended consequences. 

"Obamacare was comprehensive health reform — same thing. Instead, I favor a step-by-step approach so that we can focus on enforcement and build public confidence on that. Prove that case first and it's a pretty reasonable demand from the public that we prove ourselves on that because we've failed miserably every time that's been promised."

While both Democrats and Republicans have expressed interest in passing immigration reform in 2013, a few senators said they are opposed to aspects of the new framework. Besides Vitter, Sens. Jeff SessionsJefferson (Jeff) Beauregard SessionsGOP leaders to Trump: Leave Mueller alone FBI chief refuses to deny reports he threatened to resign amid pressure House Judiciary Chair expected to issue DOJ subpoena over Clinton emails as soon as this week MORE (R-Ala.) and Ted CruzRafael (Ted) Edward CruzCruz says Cambridge Analytica assured him its practices were legal Dem battling Cruz in Texas: ‘I can understand how people think this is crazy’ Overnight Tech: Facebook faces crisis over Cambridge Analytica data | Lawmakers demand answers | What to watch for next | Day one of AT&T's merger trial | Self-driving Uber car kills pedestrian MORE (R-Texas) have suggested they oppose parts of the framework. Sen. Mike LeeMichael (Mike) Shumway LeeOvernight Defense: Senate sides with Trump on military role in Yemen | Dem vets push for new war authorization on Iraq anniversary | General says time isn't 'right' for space corps Senate sides with Trump on providing Saudi military support Senate, Trump clash over Saudi Arabia MORE (R-Utah.), who was involved in crafting the framework, walked away from the discussions because he disagreed with creating the pathway to citizenship.