The Senate Judiciary Committee plans to introduce a criminal justice reform measure sometime this week, possibly as early as Thursday, according to several people briefed on the plans.

However, the existing legislation is believed to stop short of the sweeping overhaul being called for by some advocacy groups.

The compromise package, first reported by NPR, comes after more than two years of haggling over possible reforms, as well as mounting public pressure from both conservative and liberal groups — including those funded by the Koch Brothers, the ACLU on the left and FreedomWorks on the right — calling for broad legislation to address mounting prison costs and incarceration rates.

The bipartisan proposal is expected to address significant aspects of sentencing reform, correctional reform, re-entry programs for former prisoners and juvenile justice. It’s being spearheaded by a group of seven lawmakers said to include Senate Judiciary Chairman Charles Grassley (R-Iowa), Senate Majority Whip John Cornyn (R-Texas), Democratic Sens. Richard Durbin (Ill.), Sheldon Whitehouse (R.I.), Charles Schumer (N.Y.) and Cory Booker (N.J.) and Republican Mike Lee (Utah).

“A deal at this point seems to have been reached,” Booker said on Wednesday afternoon, adding that while the deal’s “not done till it’s done” the current proposal has his “full throated support.”

“It is good progress in the right direction,” he said.

Three people with direct knowledge of the compromise said they expect a news conference to announce its introduction on Thursday morning. Aides to several of the lawmakers involved in the talks stressed that the legislation is still being crafted and specific details have yet to be finalized.

But the measure is expected to include provisions such as allowing some prison inmates to earn early release by completing education and training programs, and expanding the judicial discretion “safety valve” in sentencing in some cases that currently require mandatory minimum sentences.

“The sentencing reforms focus on giving judges some discretion to sentence below the mandatory minimum for certain non-violent drug defendants,” said an aide familiar with the agreement.

The agreement will include many of the provisions from the CORRECTIONS ACT, a bill proposed previously by Cornyn and Whitehouse, according to an aide familiar with the agreement. That legislation would allow prisoners deemed low or medium risk to earn time credits for completing re-offender reduction programs.

A source from one of the most prominent right-leaning groups involved in criminal justice reform talks said the bill will include “more than you think, but probably not as much as people will want.”

However, the compromise is expected to stop short of many of the more ambitious reforms sought by advocacy groups on both the right and left. It is expected to include at least one provision that could cripple its chances of earning Democratic votes or of being signed into law by President Obama. The bill is expected to contain the creation of some new mandatory minimum sentences for some violent and immigration-related offenses, which could be a non-starter for some on the left.

“It’s not fair to characterize it as sweeping overhaul,” said one congressional aide who was briefed on the legislation but not authorized to address it publicly. “It is actually much less than what the advocates have been hoping for.”

The concerns that the package falls short of real reform highlights the difficult path facing any effort to overhaul the criminal justice system. Even with polls showing popular, bipartisan support for  reform, it’s unclear if it’s possible to craft a package that appeases both criminal justice advocates as well as law-and-order-oriented lawmakers. Several of the groups who have been applying pressure to lawmakers said on Wednesday they had yet to see the bill’s language and which specific reforms were proposed.

Meanwhile, the in the House, Reps. Jim Sensenbrenner (R-Wisc.) and Bobby Scott (D-Va.), have introduce legislation which contains sweeping reforms and was introduced in June. However House Judiciary Chairman Bob Goodlatte (R-Va.) and Ranking Member John Conyers (D-Mi.) plan to introduce their own legislation.

“The House Judiciary Committee is taking a step-by-step approach to address a variety of criminal justice issues through legislation…” said a House Judiciary Committee aide, not authorized to discuss pending legislation. “The committee plans to introduce legislation soon.”

Another House aide involved in that chamber’s reform efforts said that the House Judiciary Committee has also made progress on legislation that would address civil asset forfeiture, which will likely soon be introduced.

Matea Gold and Max Ehrenfreund contributed to this report.