Florida Senator Marco Rubio is warning fellow conservatives that the bipartisan immigration reform bill currently being debated in Congress is far better than the alternative: letting President Obama legalize undocumented immigrants by executive order.

Last year, Obama unilaterally enacted the Deferred Action for Childhood Arrivals program, which offered a path to citizenship and a halt to deportations for some young undocumented immigrants brought to the United States as children.

By and large, that was a popular move, and one that many conservatives not say they support. But Rubio cautions that Obama won't stop there if the House of Representatives refuses to pass the current immigration reform bill.

"I believe that this president will be tempted, if nothing happens in Congress, he will be tempted to issue an executive order as he did for the DREAM Act kids a year ago, where he basically legalizes 11 million people by the sign of a pen," Rubio told "The Morning Show with Preston Scott" Tuesday morning.

"We won't get any E-Verify. We won't get any border security. But he'll legalize them. What I've tried to do is come up with as best as possible, given who controls the Senate, a way to start this conversation to at least begin to address some of these issues," Rubio said.

The comprehensive immigration reform plan passed by the Senate offers a path to citizenship for most of the 11 million undocumented immigrants in the country. However, that offer is tempered by strict requirements and fees, as well as increased spending on border security and employment verification, concessions demanded by more moderate Republicans like Rubio.

But many conservative and Tea Party-affiliated members of Congress are opposed to any kind of immigration reform and are willing to forgo the concessions in order to prevent the bill's passage. Rubio urged them to reconsider, painting a nightmare (for Republicans) scenario.

"Unless we're going to try to round up and deport 11 million people -- something that not even the most vociferous opponent of the bill proposed -- then we are going to have to at some point address this issue. We can't leave, in my mind, the way it is," Rubio said.

"Because I think a year from now we could find ourselves with all 11 million people here legally under an executive order from the president, but no E-Verify, no more border security, no more border agents, none of the other reforms that we desperately need."