WASHINGTON — The Senate is poised as early as Tuesday to act on a Trump-backed measure to end the partial government shutdown, but a bill promoted as a compromise to pair the president’s wall with legal protections for some immigrants would also severely restrict migrants’ ability to claim asylum, drawing fierce opposition from immigrant rights groups.Senator Mitch McConnell, Republican of Kentucky and the majority leader, is planning on Tuesday to put the measure on the Senate’s agenda, setting up a likely vote on Thursday, absent any agreement from Democrats to act on it sooner. But its prospects in the Senate are dim, and with the shutdown now in its fifth week, 800,000 federal workers are almost certain to miss their second paycheck on Friday.The 1,031-page bill, made public on Monday evening by the Senate Appropriations Committee, would fund shuttered federal agencies through the end of the fiscal year. It includes $5.7 billion for the border wall that Mr. Trump has proposed and large increases for detention of and removal of immigrants, as well as three-year provisional protections for 700,000 of the young undocumented immigrants known as Dreamers, and 300,000 immigrants mostly from Latin American countries who have been living in the United States under Temporary Protected Status.But while Republicans say the protections are drawn from the Bridge Act, a bipartisan measure, that bill would in fact protect hundreds of thousands more Dreamers, who were brought to the United States illegally as children. The Republican proposal would shield only those who applied for and received work permits under Deferred Action for Childhood Arrivals, or DACA, created by President Barack Obama, which Mr. Trump rescinded in 2017.[Senate leaders have reached a deal that can end the government shutdown by the weekend.]Federal court decisions have kept DACA in place, and on Tuesday, the Supreme Court again declined the Trump administration’s request to review the legality of the program, almost certainly keeping it in place for the rest of the year. That decision by the court significantly devalued Mr. Trump’s overture to Democrats resisting wall funding.The new Senate measure also includes several provisions that are meant to make it more difficult for migrants to claim asylum in the United States, a legal process that allows people fleeing violence and persecution in their home countries to seek refuge. The changes have been top priorities of Stephen Miller, the conservative White House aide who crafted much of Mr. Trump’s immigration agenda.It would bar Central American children from seeking asylum in the United States, instead requiring them to apply in their own countries, in what the legislation describes as a program that “reduces the incentive for such persons to make the dangerous journey to the United States southern border to request asylum.”But Democrats and immigrants’ rights advocates denounce the plan as cruel. While the Obama administration created a similar program to expedite the claims of Central American children seeking asylum, it never moved to block such minors from applying inside the United States.“These are children who are often desperately fleeing terrible violence back home,” said Representative Diana DeGette, Democrat of Colorado. “They are literally running for their lives and asking for our country to help. Instead of offering them help, this proposal would require border officials to turn a deaf ear to their desperate pleas and send these kids back to the very places they just risked their lives to escape.”A separate provision would allow immigration authorities to quickly remove Central American minors seeking asylum in the United States, a change to an anti-child-trafficking statute that some scholars said would violate international law.“In effect, we are looking at the rapid expulsion of these children,” said Greg Chen of the American Immigration Lawyers Association. “The effect of the law will be to send people back into harm’s way, which would be a violation of international law.”The measure also adds a high bar for asylum claims across the board, mandating that they be deemed “in the national interest.” It would introduce a host of new grounds for deeming an asylum claim “frivolous,” including if the migrant seeking protection was also trying to obtain work authorization, had used a fraudulent document — knowingly or unknowingly — or did not file in a timely way.Republicans are arguing that the bill would do precisely what Democrats have been demanding: reopen the federal government immediately. As an added sweetener to Democrats, the measure also includes $12.7 billion for disaster relief, and would renew the Violence Against Women Act, which authorizes and funds services for victims of domestic violence — and expired at the end of last year.But the Senate math does not work in Mr. McConnell’s favor. He would need seven Democrats to join with all 53 Republicans for the measure to pass. But there are no more than a handful of Democrats in Republican-leaning states — Senators Kyrsten Sinema of Arizona, Doug Jones of Alabama and Joe Manchin III of West Virginia — who might vote in favor.A spokesman for Mr. Manchin said the senator would remain undecided until he saw the text of the measure. Ms. Sinema and Mr. Jones have not announced their intentions.House Democrats are also planning this week to bring up a package of legislation to reopen the government and provide some funding for border-related operations, including infrastructure improvements at ports of entry and immigration judges. They are still weighing whether to bring up their own border security proposal as part of a measure to fund the Department of Homeland Security. But given that none of their plans include money for a wall, Mr. McConnell has said he will not bring them up in the Senate.