Reps. John Carter of Texas and Raul Labrador of Idaho both separately said the time for negotiations is over.

“Tomorrow night, as far as I’m concerned, is the last night I’m gonna meet,” Carter said.

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Labrador, a key conservative in the group, agreed.

“I think it’s time for us to move ahead with a Republican plan if nothing happens tomorrow,” Labrador said. He characterized such a plan as “conservative immigration reform.”

That the House’s eight-person bipartisan group appears to be breaking down is a major development in the immigration debate. If the House does not come out with its own plan, it will make immigration reform a lot more difficult. The theory from Republican leadership was that the bipartisan group’s product would give the House GOP buy-in.

If the Republicans release a conservative immigration plan, it will most likely not include a lot of the concessions the group made to Democrats, sources said.

The group has been hung up over how the legislation deals with the health care of newly documented workers and worker visas. Some Democrats also don’t like a trigger that would shut down the legalization process if an employee verification system is not in place.

The health care issue is chief among the outstanding issues. Republicans want immigrants on the pathway to citizenship to provide their own health care. Democrats prefer Senate language, which says immigrants on the pathway cannot receive health care subsidies.

Republicans and Democrats in the group have agreed on “95 percent” of an immigration bill, Carter said. A key Democratic negotiator, Illinois Rep. Luis Gutierrez, agreed, saying Wednesday that the group was “not far” apart in its talks.

( PHOTOS: 20 quotes on immigration reform)

Democrats say they have no plans to walk. When asked about the Republicans’ comments, Gutierrez said he was still “very confident,” saying he expected Thursday’s meeting to be “fruitful.”

”I’m very optimistic about tomorrow and looking forward to seeing my dear friends,” he said. “We’ve shared so many wonderful dinners together … Regardless, we will have a friendship that will endure forever.”

Seung Min Kim contributed to this report.