Democrats will formally file President Biden’s immigration bill on Thursday, facing steep odds as they attempt to create the first major path to U.S. citizenship for undocumented immigrants in nearly 35 years.

The bill is the centerpiece of Biden’s broad strategy to forge a more humane immigration system, and it would grant legal status to approximately 11 million people, mostly from Mexico and Central America.

The legislation faces significant hurdles in a divided Senate still reeling from the impeachment trial of former president Donald Trump, who often tapped into anti-immigration rhetoric to fire up his campaign rallies.

Biden has expressed hope for passing a bipartisan measure, and the U.S. Citizenship Act marks the first major effort since the Senate passed a massive immigration overhaul in 2013 and that effort died in the House. But it is unclear how aggressively he will court Republicans needed to pass the Senate.

The U.S. government has not passed a major citizenship bill since 1986, when amnesty legislation signed by Republican President Ronald Reagan legalized nearly 3 million undocumented immigrants.

“If Republicans want to come forward and work on immigration, I think the president is open to working with anyone who wants to get something done and get a bill to his desk,” said a senior administration official, who like others spoke on the condition of anonymity Wednesday to discuss the early negotiations. “We’re open to a conversation with anyone about this, but we think this is a much more comprehensive way to deal with this issue than just simply a wall.”

Biden indicated at a CNN town hall Tuesday night that he is open to alternate routes to citizenship — such as stand-alone bills that would legalize smaller groups of immigrants such as farmworkers — but he called the bill “a reasonable path to citizenship.”

Republicans have signaled little support for Biden’s approach. Sen. Marco Rubio (R-Fla.), a backer of the 2013 bill, called the latest measure a “blanket amnesty.” Sen. Mitt Romney (R-Utah), who voted with Democrats to convict Trump, touted his own measure this week that would increase the minimum wage “while ensuring businesses cannot hire illegal immigrants.”

“We must protect American workers,” Romney said in a tweet Tuesday.

Biden’s bill includes some enforcement provisions such as increased border technology to interdict drug traffickers and smugglers, higher penalties for employers who exploit undocumented laborers in the United States, and increased funding for immigration courts.

But E-Verify, which checks a person’s legal status to work in this country, “will not be mandatory” for U.S. employers, and Biden has said he would not expand the border wall.

Mainly the bill takes an expansive approach: It promotes integration of immigrants and refugees, reduces years-long backlogs to immigrate to the United States, and creates two major pathways to citizenship for undocumented immigrants.

Farmworkers, immigrants who arrived in the United States as children, and people with temporary protected status — granted to those whose homelands are deemed too dangerous to return to — would have the fastest route to naturalization. They would immediately become eligible for green cards and could apply for citizenship after three years.

Millions of other undocumented immigrants would be allowed to apply for citizenship after eight years, longer than the current five-year requirement but shorter than the path the Senate approved in 2013.

All applicants must pass background checks and have been in the United States as of Jan. 1, a requirement intended to discourage a migration surge to the southwestern border.

Biden has characterized his bill as a way to reimagine immigration in the United States after the Trump administration clamped down on it, and the measure addresses details such as replacing the word “alien” with “noncitizen.” Where his predecessor often cast immigrants as criminals, Biden’s White House calls them “neighbors, colleagues, parishioners, community leaders, friends, and loved ones.”

Biden tapped the children of immigrants to shepherd his immigration bill through Congress. Bill sponsors are Rep. Linda T. Sánchez (D-Calif.), the sixth of seven children raised by Mexican immigrants in Southern California, and Sen. Robert Menendez (D-N.J.), the son of Cuban immigrants raised in a tenement in Union City, N.J.

Advocates for immigrants cheered plans to formally introduce the bill, the broad outlines of which Biden sent to Congress on his first day in office, but said they doubted it would pass. Democrats hold the House, but they need at least 10 Republican votes to reach the 60-vote threshold to pass the Senate.

Advocates and dozens of lawmakers are urging Senate Democrats to instead legalize at least 5 million undocumented immigrants this year through the budget reconciliation process, which requires a simple majority to pass. That group would include essential workers, immigrants who arrived as children and people with temporary protected status.

Erika Andiola, an immigrant from Mexico whose relatives faced deportation under the Obama administration, called the Biden bill “a good symbolic gesture, but it’s not enough to protect people like me, my family and my community.”

Frank Sharry, executive director of America’s Voice, an advocacy organization, said passing citizenship through reconciliation is “the best shot we have this year.”

“There is a point where Joe Biden is going to have to decide,” said Nicole Melaku, executive director of the National Partnership for New Americans, a coalition of immigrant advocacy groups. “There is a moment where every disposable tool in his toolbox will need to be pulled out whether or not Republicans come along.”

Senior administration officials who promoted the bill late Wednesday repeatedly declined to say whether they are considering using the reconciliation process to pass citizenship.

“It’s just too early to speculate about it right now,” the aide said.

Matt Viser contributed to this report.