Sen. Marco Rubio (R-Fla.) Sen. Marco Rubio (R-Fla.)

The path through Congress for a comprehensive rewrite of the nation’s immigration laws appeared murky Wednesday, as key backer Sen. Marco Rubio (R-Fla.) emerged from a meeting with conservatives in the House to say the measure he helped write cannot pass the Republican-held chamber.

“The bottom line is there’s a vibrant debate going on in the Republican Party. But I can tell you that the bill as it is currently structured isn't going to pass the House. And I think will have trouble passing the Senate," Rubio said, after a meeting in the basement of the Capitol with members of the Republican Study Group, the House's most conservative caucus.

Rubio attended the meeting along with Sen. Jeff Flake (R-Ariz.), another supporter of the Senate measure. They sat on a panel with Republican senators opposed to the bill, including Ted Cruz (Tex.), Mike Lee (Utah) and Jeff Sessions (Ala.), for what members said was a full airing of Republican thought on the immigration issue.

House Majority Leader Eric Cantor (R-Va.) and key House Budget Committee Chairman Paul Ryan (R-Wis.) also attended the closed-door briefing.

As the meeting broke, supporters of the measure did not appear to have swayed many House conservatives to support the Senate bill’s central plank — a path to citizenship for the estimated 11 million people now living in the country illegally.

“For my constituents, it’s easier to explain a path to status than a path to citizenship, particularly if that path involves jumping ahead of people who have been doing it the way we’ve told them to do it," Rep. Trey Gowdy (R-S.C.), chairman of a key House subcommittee, said after the meeting.

Many also seemed skeptical of the comprehensive approach led by the bipartisan eight-member Senate group that crafted the measure, preferring a package of bills that would address different pieces of the immigration issue separately. That approach has been championed by the chairman of the House Judiciary Committee, Rep. Bob Goodlatte (R-Va.).

The Senate will open debate on the bill authored by the so-called Gang of Eight next week, beginning an expected weeks-long floor debate over amendments to the legislation.

Advocates are growing increasingly wary that Republicans will push the bill further to the right on the Senate floor -- only to see the House GOP ditch the hard-fought Senate compromise and start over with their own piecemeal approach.

Rubio has been increasingly insistent that the bill he helped write will need changes to pick up the Republican support necessary to get the 60 votes it will need to pass the Senate. He wants to strengthen pieces of the bill that would require the Department of Homeland Security to write a plan to secure the border before illegal immigrants could seek to normalize their status.

"We certainly are going to have to do more than what’s in the bill now in order to get the votes necessary to pass a law," Rubio told reporters.