TUCSON, Ariz. — The immigration crisis in Arizona’s second-largest city plays out five days a week as grim-faced US Marshals escort groups of up to 75 migrants, handcuffed and shackled at the waist and ankles, into a grand second-floor courtroom in a downtown federal building.

Most are from Central America, and all are charged with illegal entry. They are tried together, appearing before a federal magistrate — seven at a time — under Operation Streamline, a fast-track prosecution process to crack down on migrants and leading to quick deportation.

The program, labeled “assembly-line justice” by critics, has emerged as an important tool for President Trump, who recently doubled down on promises to begin deporting “millions” of migrants facing deportation.

On Saturday, Trump tweeted that he would delay for two weeks Sunday’s scheduled deportation raids on 2,000 families living in the US illegally, “to see if the Democrats and Republicans can get together and work out a solution to the Asylum and Loophole problems at the Southern Border.”

Earlier on Saturday, House Speaker Nancy Pelosi had urged Trump to stop the raids.

In Arizona, migrants are usually tried within days of crossing the border. From Monday to Thursday, they shuffle into the large second-floor courtroom.

On Fridays, that courtroom is reserved for very different proceedings — the naturalization ceremonies of dozens of migrants, most from Mexico and Central America, who used legal means to stay in the US.

Many wear flowery dresses and neatly pressed suits, waving small paper American flags. By the end of the ceremony, many are in tears as they utter the final words to the Pledge of Allegiance — “One nation under God, indivisible, with liberty and justice for all.”

Tears also flow from the eyes of their compatriots the other days of the week. People who shared the same dream, but not the same methods, and now await justice as accused illegal border-crossers.

Operation Streamline, a Justice Department and Department of Homeland Security program, was rolled out in Del Rio, Texas in 2005 to expedite deportations, reduce the hearing backlog, and deter would-be migrants from entering the US illegally. It has since spread to a handful of other cities along the southwest border. In Tucson, it has recorded an average 12,400 prosecutions a year for the last five years, the Arizona Daily Star reported.

Migrants who are caught illegally crossing the border by US Customs and Border Protection agents are immediately charged with a criminal offense. First-time offenders are prosecuted for misdemeanors for illegal entry, which carries a maximum six-month sentence. Those who have been deported in the past can be charged with a felony and sentenced for up to two years. Those with a criminal history face up to 20 years in prison.

On Friday, The Post saw 28 migrants from Mexico, Guatemala, Belize and Ecuador tried in a third-floor courtroom while the regular Operation Streamline courtroom was used for naturalization proceedings. One attorney called the day “Streamline Light” because only 28, as opposed to 75, were tried in a single session.

The migrants, who included one woman from Mexico, were dressed in dusty T-shirts and jeans — the same clothes they were wearing during their journeys to the border. One man wore camouflage. A strong smell of sweat pervaded the courtroom.

None of the migrants spoke English, and they listened to judge D. Thomas Ferraro’s instructions in Spanish translation on headsets, their court-appointed attorneys standing behind them. All answered “si” or “culpable” — “guilty” in Spanish — when asked to plead.

The migrants were immediately sentenced, with terms ranging from 30 to 75 days.

The trials lasted less than 30 minutes.

Those who had already served time were immediately handed over to ICE agents and would be deported within the next few days, flown to their home country as soon as ICE has a planeload of migrants ready to go.

The others would be driven to a correctional facility in nearby Florence, Ariz.

“It’s difficult to do as an attorney,” said Jay Sagar, 43, an assistant federal public defender, who has worked on Operation Streamline cases in Tucson for the last 11 years. “You see a lot of tragedy. Most of my clients break down in tears when I meet them because they realize that they have reached the end of the road.”

Attorneys typically meet their clients in the morning before the migrants face the judge in the afternoon — a situation that has led to criticism from the American Civil Liberties Union. The organization said migrants “frequently have no counsel until their hearings, allowing little time to consult an attorney to understand the charges and plea offers, consequences of conviction and potential avenues for legal relief.”

But one court-appointed attorney who has worked for several years representing Operation Streamline clients says the migrants are well-represented.

“We get plenty of time to talk to them,” said Wanda Day. “Most of my clients understand what is going to happen to them when they enter that courtroom, and I think the prospect of spending time in jail is preventing them from trying to come back.”

Migrants can try to avoid deportation by asking for asylum once they cross the border. But it doesn’t prevent them from being criminally prosecuted for illegal entry, Sagar told The Post, adding that migrants can only begin the lengthy asylum process — it typically takes three years to wind its way through immigration courts — after serving their jail time.

Migrants seeking asylum undergo interviews with federal agents within days of crossing the border. The agents determine if their claims pass a “credible fear” test that allows them to enter into the lengthy legal process.

But the deportation process can be swift.

“If you have no prior deportations or a criminal history, you can be deported right after you serve your prison time,” Sagar said.

And if the program was set up to deter migrants from attempting to cross the border with quick prosecutions, it is not working, said Sagar, who has seen many repeat clients.

“What is the number of days that you will sit in jail that will stop you from coming?” said Sagar. “It’s not enough to strike fear in someone who is so desperate to create a better life for their family.”