Ahead of the expected release Tuesday of a sweeping bipartisan proposal to revamp the nation’s immigration laws, faith-based and civil liberties groups began calling for changes, singling out the proposed path to citizenship for illegal immigrants as too stringent, while a key Republican senator said lawmakers need to be “realistic” about creating such a path.

President Obama described the bill in a late-afternoon statement Tuesday as “clearly a compromise” and cautioned that “no one will get everything they wanted, including me.” But after being briefed on the bill by Sens. Charles E. Schumer (D-N.Y.) and John McCain (R-Ariz.), he said it was “largely consistent” with his principles for comprehensive reform.

“This bill would continue to strengthen security at our borders and hold employers more accountable if they knowingly hire undocumented workers,” Obama said. “It would provide a pathway to earned citizenship for the 11 million individuals who are already in this country illegally. And it would modernize our legal immigration system so that we’re able to reunite families and attract the highly-skilled entrepreneurs and engineers who will help create good paying jobs and grow our economy.”

He said most Americans support these “common-sense steps,” and he pledged to “do whatever it takes to make sure that comprehensive immigration reform becomes a reality as soon as possible.”

Schumer said after the meeting that while Obama has some reservations, “he was very supportive of the bill we have put together and simply wants to make sure we keep moving it along and get something done.... So we’re feeling very good about this, and we’re moving in a very, very good way.”

Said McCain: “This is the beginning of a process, not the end. We will have hearings, we will have amendments, we will have floor debates. But I’m confident that at the end of day, we’ll have a bill on the president’s desk because all the major players involved in this issue are now on board.”

Among those calling for changes was Anthony D. Romero, executive director of the American Civil Liberties Union.

“While this legislation is certainly a breakthrough, it will have to be improved to address severe obstacles for many aspiring citizens,” he said. “The roadmap to citizenship should not exclude people based on minor crimes or people who can’t afford hefty fines.”

Bishop Ricardo McClin, who belongs to PICO National Network, a national faith-based organizing group, said: “Unfortunately, the proposed legislation falls short by placing unnecessary obstacles and delays in the path to citizenship and could unfairly exclude some of the 11 million aspiring Americans who are our neighbors, friends, family and fellow-worshipers.”

Meanwhile, gay-rights advocates expressed disappointment that the proposal did not include a new category of visas for same-sex foreign national spouses of U.S. citizens, who are not able to apply for such visas under current laws. The advocates plan to push for the addition during the amendment process.

“We’re disappointed that we’re not in the base but we’ve always known that our best shot would be at the committee level,” said Fred Sainz, spokesman for the Human Rights Campaign. “The goal is to get into the underlying bill. How that happens is not as important as the fact that it happens.”

On Capitol Hill, Sen. John Cornyn (R-Tex.), a longtime proponent of enhanced border security and immigration reform, said lawmakers needed to be “realistic” about creating a decade-long path to citizenship. Such a plan, Cornyn said, requires lawmakers to make “promises that may or may not be possible to keep.”

“Here’s the challenge, it really is a question of trust,” said Cornyn, the top Republican on the Senate Judiciary Committee’s Immigration, Refugees and Border Security Subcommittee. “The present Congress can’t bind future congresses, nor the current president bind future presidents, so I think we need to be realistic in terms of what this present Congress could bind future congresses to, in terms of goals five years and 10 years out.”

Cornyn added that it was time for Congress to tackle the reform and warned that the process would need to be open and transparent over several weeks to build credibility.

“No one I know believes that the status quo is acceptable … but openness; this is essential to gaining public confidence in the content of the bill. We know it’s complicated,” he said. “I can’t see any reason to undermine confidence by trying to jam it through without adequate time for people to read it and to hear from their constituents.”

A bipartisan group of senators is expected to release broad legislation later Tuesday that would overhaul the nation’s immigration laws by offering a path to citizenship for millions of illegal immigrants, directing billions of dollars to bolster border security, and creating tens of thousands of new visas for foreign workers in low-skilled jobs, according to a summary obtained by The Washington Post.

The bill, which is hundreds of pages long, is the culmination of a months-long effort from the so-called “Gang of Eight,” a coalition of four Republicans and four Democrats who have been hashing out the details of a proposal in consultation with business and labor leaders, as well as other interest groups. The release of the legislation will mark the first time since 2007 lawmakers have undertaken an effort to pass comprehensive immigration reform. The 2007 plan was killed in the Senate.

“We commend the bipartisan ‘Gang of 8’ senators for putting forward a bill that addresses the big challenges we have identified for getting U.S. immigration policy right,” said Greg Brown, chairman and chief executive officer of Motorola Solutions, Inc. and head of Business Roundtable, an association of top corporate executives.

The soon-to-be-released measure would allow most undocumented immigrants who arrived in the country before Dec. 31, 2011, to immediately gain “registered provisional” status after paying a $500 fine and back taxes, provided they have not committed a felony or three misdemeanors.

They could then apply for permanent resident status in 10 years after paying additional fees. Three years later, they could apply for citizenship, according to the plan summary. The fastest path to full citizenship would take 13 years, according to the legislation, but it could take longer in some cases, Senate staffers said.

The bill will also require the government to implement strict new border-control measures — including up to $7 billion in new surveillance drones, fencing, border guards and workplace tracking systems — before the undocumented immigrants are granted green cards. The bill stipulates that the government must surveil 100 percent of the border and apprehend 90 percent of the people trying to enter illegally in high-risk sectors.

The release of the bill is expected to spark a new round of debate over what’s proven in recent years to be a politically contentious issue. While some Republicans have called for the party to involve itself in a reform effort, others have opposed it, charging that a path to citizenship amounts to amnesty.

There is a political imperative for the GOP to embrace immigration reform. Obama won Latino voters by a whopping 44 points in 2012, exit poll data show, stoking GOP concerns that the party’s perceived hostile posture toward immigrants would continue to imperil its chances with a growing share of the electorate.

The White House said Monday that Obama is pleased with what he’s seen from the “Gang of Eight” so far and plans to review the legislation.

“We remain cautiously optimistic that this progress will lead to legislation that can pass and the president can sign,” White House press secretary Jay Carney told reporters Monday.

Senators had originally planned a high-profile rollout of their measure, including a Tuesday morning news conference where they would be flanked by immigration reform advocates. But the group opted to postpone the event late Monday because of bombings at the Boston Marathon.

Reaction to the emerging details of the proposal was muted on Capitol Hill Tuesday morning as lawmakers paused to pay respects to victims in Boston.

Rep. Steve King (R-Iowa), who has long been critical of loosening immigration restrictions, suggested to National Review that the attack in Boston should delay reform efforts.

“Some of the speculation that has come out is that yes, it was a foreign national and, speculating here, that it was potentially a person on a student visa,” King said. “If that’s the case, then we need to take a look at the big picture.”

The bill also aims to clear a backlog of more than 4 million foreigners around the world who have applied for family-based visas to be reunited with relatives in the United States.

But the proposal would also put more emphasis on “merit-based” work skills than on family ties over the ensuing years.

The bill proposes eliminating 70,000 green cards reserved for brothers, sisters and adult married children of U.S. residents, as well as a diversity lottery aimed at giving green cards to people selected at random from foreign countries each year.

The Senate Judiciary Committee has scheduled hearings for the measure on Friday and Monday. Opponents are expected to offer amendments aimed at undercutting it.

Sen. Jeff Sessions (R-Ala.), a leading critic of the reform effort, charged in a statement Tuesday that the schedule of Senate Judiciary Committee Chairman Patrick J. Leahy (D-Vt.) was evidence that Democrats are trying to jam through the reform measure.

“Chairman Leahy’s decision to now hold two hearings in two days — on one Friday, one on Monday — is only further proof of the majority’s desire to rush this bill with minimum public scrutiny,” said Sessions.

Sen. Marco Rubio (R-Fla.), a member of the “Gang of Eight,” said in a round of interviews over the weekend that he looks forward to getting input from his Senate colleagues. But, he cautioned, he’ll oppose amendments designed to kill the measure.

“We are going to get ideas that make it better,” Rubio said on NBC’s “Meet The Press.” “And I welcome that. Now, there are amendments designed to undermine this. There are amendments that will be designed to make this thing undoable. And obviously, I’ll oppose those, especially if that’s the intent of them.”