Rep. Paul Ryan (R-Wis.) has endorsed Florida Sen. Marco Rubio's immigration plan in a Facebook post, a high-profile endorsement from a potential rival.

"Senator Rubio is exactly right on the need to fix our broken immigration system," Ryan wrote on his Facebook page. "I support the principles he’s outlined: modernization of our immigration laws; stronger security to curb illegal immigration; and respect for the rule of law in addressing the complex challenge of the undocumented population. Our future depends on an immigration system that works."

Rubio has not introduced a bill detailing his immigration policy. He told the Wall Street Journal that he doesn't support a special pathway to citizenship for undocumented immigrants, but that they should be allowed to stay: "They would have to pay a fine, pay back taxes, maybe even do community service." Most would then be able to apply for permanent residency and possibly citizenship, but "they'd get behind everybody who came before them" in line. The plan already faces some pushback from conservatives who see it as another form of amnesty.

Both Rubio and Ryan are considered likely presidential candidates.