Republican members of the bipartisan group drafting Senate immigration legislation are expected to brief Senate Republicans Wednesday on the details.

“Tomorrow we will have a conference discussion about the bill,” said Sen. Jeff Flake, R-Ariz., one of the four Republicans in the working group. “We have a regular [Wednesday] policy meeting at lunch and it will be discussed at that time.”

Asked if the full details of the bill would be provided, Flake said, “such as we have.” Members have not yet received the legislative language back from staff who are drafting it, so it’s unclear how thorough the briefing will be, according to a source.

Sen. John McCain, R-Ariz., said it was a possibility, but added that it would depend on “whether we have it completed.”

Sen. Charles E. Schumer, D-N.Y., also a group member, said “I believe we are on track” to produce a bill by the end of the week.

The Democratic members of the group spoke at their caucus luncheon Tuesday and “provided an update on the process,” according to a Senate Democratic source.

The group has been working on the bill behind closed doors since January and has been criticized by some senators for not sharing details of the developing measure.

Sen. Jeff Sessions, R-Ala., who has been chief among those critics, said he was disappointed that the Judiciary Committee, which has jurisdiction over the issue and of which he is a member, will not get an advance glimpse of a bill they will have to consider before the entire Senate will.

“It’s a disappointment,” Sessions said. “The system doesn’t work well when a small group of senators produce a product and you have a very short period of time to review it.”

His comments come after Sen. Charles E. Grassley, R-Iowa, ranking member of the Judiciary Committee, wrote to the Republican members of the group of eight asking that their staff be put in contact with GOP committee staff by the end of Monday.

That never happened, and instead the entire conference will get the details at Wednesday’s policy lunch.