Sen. Marco Rubio (R-Fla.) threw his full weight Sunday behind a sweeping immigration measure he's been working to develop as part of a bipartisan group of senators, giving the soon-to-be released proposal a boost as lawmakers prepare for the next phase of the legislative process.

"We've been working very hard and I think we have come to a position now where we've been able to tell our staff to draft something. We need to read that, and that's what we're in the process of doing," Rubio said on ABC News's "This Week With George Stephanopoulos."

Rubio is part of the so-called "Gang of Eight," a bipartisan group that has been developing a broad proposal to revamp the nation's immigration laws. Winning his support has been seen as key by the group, which hopes to eventually convince other Republicans to support it.

Appearing on all five Sunday news shows as well as programs on Spanish-language channels Telemundo and Univision, Rubio said the group would offer more details about its plan later in the week. Sen. Charles E. Schumer (D-N.Y.), who is also in the "Gang of Eight," said the group expects to unveil its proposal on Tuesday.

" I look forward to us being able to talk in more detail later this week about that. I’m very optimistic about it," Rubio said on CBS News's "Face The Nation."

After the bill is unveiled, the Senate Judiciary Committee is expected consider it. There, senators can offer amendments as the debate unfolds.

Two weeks ago, after business and labor leaders appeared to clear the last major policy hurdle in the negotiations when they agreed to terms on a new guest-worker program, other members of the "Gang of Eight" signaled that a deal was all but complete. But Rubio made clear that he wasn't on board just yet, raising questions about whether he'd walk away from the talks.

He put those questions to rest on Sunday.

"I just hope that I can convince people that leaving things the way they are now is much worse thanthan approaching it the way we've outlined," he said.

The measure is expected to include a path to citizenship for illegal immigrants, new visa programs for low-skilled and highly skilled workers, increased border control and workplace security measures, and the elimination of some categories of family visas.

"This is a very balanced bill," Schumer said on ABC News.

The idea of a path to citizenship has riled some conservative lawmakers. Rubio sought to reassure the public Sunday that any path would be tied to tightening border security and explained that the process would not be easy.

"We're not awarding anything. All we are giving people the opportunity to eventually do is gain to access to the same legal immigration system, the same legal immigration process that will available to everybody else," Rubio said.

Sen. John McCain (R-Ariz.), a third member of the "Gang Of Eight," who said he is "guardedly optimistic" about the prospect of passing broad reform, noted conservatives have raised questions about the proposal.

"A lot of my conservative colleagues have significant questions and they are legitimate," McCain said on CNN's "State of The Union."

Sen. Jeff Sessions (R-Ala.) offered concerns about the measure on "This Week." "I really respect the work of the work of the 'Gang of Eight,' but they have produced legislation it appears ... that will give amnesty now, legalize everyone that's here effectively today, and then there's a promise of enforcement in the future," he said.

Sen. John Cornyn (R-Texas), the Senate's second-ranking Republican, said he was "encouraged" by what the "Gang of Eight" has come up with, but is reserving judgement on the measure until after he reads it. Border security, Cornyn said, must be adequately addressed to win his support.

"I believe border security is absolutely critical to this picture," Cornyn said on "Fox News Sunday."

Rubio said he is eagerly anticipating the chance to give all senators an opportunity to weigh in on the measure.

"I am looking forward to the other 92 senators weighing in because I think we are going to make it better," he said.

Updated at 11:40 a.m.