Congressional Democrats are saying a comprehensive immigration deal is in sight, but Republicans are cautioning that any talk of a deal is premature. NBC's Kristen Welker reports.

With the caveat that negotiators still need to review and agree on legislative language, two key Senate lawmakers said Sunday that a deal on a comprehensive immigration reform bill is close but not complete after a breakthrough in talks between business and labor groups this weekend.

"With the agreement between business and labor, every major policy issue has been resolved on the Gang of Eight," said Democrat Sen. Chuck Schumer, one of the eight Senate leaders working on the legislation, during an interview on NBC's Meet the Press.

Noting that the group has pledged not to come to a final agreement until legislative language is finalized, Schumer said he is "very, very optimistic" that the group of lawmakers will have a deal by next week.

Republican Jeff Flake of Arizona, also a member of the Gang, agreed that lawmakers will be focused on the exact wording of the bill.

"We've still got a ways to go in terms of looking at the language and making sure that it's everything we thought it would be," Flake said on NBC. "But we're closer, certainly."

Another member of the group, Republican Sen. Lindsey Graham of South Carolina, said on CNN that negotiators have a 'conceptual' agreement.

"It’s got to be written up," he said. "We haven’t signed off; there’s a few details yet. But conceptually, we have an agreement between business and labor, between ourselves. It has to be drafted. It will be rolled out next week"

After the Chamber of Commerce and the AFL-CIO reached an agreement on the parameters of a guest worker program -- one of the main holdups in the negotiations -- Republican Sen. Marco Rubio warned that reports of an overarching Gang of Eight deal were "premature."

Schumer said Sunday that Rubio's statement did not indicate any kind of disagreement within the Senate group.

"As Senator Rubio correctly says, we have said we will not come to final agreement until we look at all the legislative language, and he's correctly pointing out that language hasn't been fully drafted," Schumer said. "There will be little kerfuffles but I don't think any of us expect there to be problems."

Rubio, the son of Cuban immigrants whose biography and conservative credentials make him a key GOP voice on immigration, also wrote in a letter to Senate Judiciary Committee Chairman Patrick Leahy and again in a press statement early Sunday that proponents should not rush the legislation to passage.

"Arriving at a final product will require it to be properly submitted for the American people’s consideration, through the other 92 senators from 43 states that weren’t part of this initial drafting process," Rubio said. "In order to succeed, this process cannot be rushed or done in secret.”

Flake echoed that sentiment Sunday, pledging that the draft legislation will be amended in the Senate Judiciary Committee process and on the Senate floor.

"There will be input, there should be input," Flake said. "It will make it a better product."

Schumer rejected the notion that Rubio could break from the Gang of Eight over concerns about the process.

"He is protecting some of the things that he thinks are very important in the bill, but I don't think that will stand in the way of any final agreement," Schumer said. "I think we're all on track."

Calling Rubio is "extremely important" to the bipartisan coalition, Flake said he's confident that the Gang of Eight will remain united.

"I think that we'll stick together as a Gang," he said. "And I hope that we can pull some Republicans our way. I think a number of them are with us already."

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