CIUDAD JUAREZ, Mexico — This gritty, industrial city on the banks of the murky Rio Grande is bracing for the Trump administration to dump thousands of migrants from Central America and other lands here under a new agreement to curb mass migration to the United States. But frantic Mexican officials say they likely cannot handle the rapid influx, as they are desperate for more shelter space, food and supplies.

With days to prepare, a top state official said he expects a fivefold increase in the number of migrants who will be sent to Juarez as a result of the expansion of the Trump administration’s Migrant Protection Protocols. The program, which is under court challenge, sends migrants who are seeking refuge in the United States back across the border into Mexico to await their asylum hearings.

More than 200 migrants were sent back to Juarez on Thursday, double the previous day, and officials expect as many as 500 migrants each day will be returned from El Paso to Juarez in coming weeks.

“We didn’t expect this many, but it’s our job and we’re trying to handle the situation,” said Enrique Valenzuela, head of the Chihuahua State Population Council, which registers migrants in Juarez. Valenzuela said Mexico’s federal government brokered the deal to accept the migrants with the White House, part of a diplomatic effort to avoid President Trump’s threatened tariffs on Mexican goods. “We had no say. We had no choice.”

Returning migrants from the United States into Mexico is the cornerstone of an agreement between the two countries to stanch historic flows of migrant families and unaccompanied minors into the United States. Migrant families with young children are overwhelming almost all aspects of the U.S. immigration system and are frustrating Trump’s campaign promises to block illegal immigration.

The agreement already is testing the infrastructure in Juarez, a city that is crowded and lacking in shelter space. Juarez has about a dozen migrant shelters — most run by churches — with room for 1,500 people.

That many people could be turned away from the U.S. border every few days, and Valenzuela said the city could use 20 to 30 more shelters to house potentially thousands more migrants.

Valenzuela estimated that as many as 70,000 migrants could be returned from the United States to Juarez this calendar year, a number that would equate to about 5 percent of the city’s population. Borderwide, Mexico has accepted about 10,000 migrants this year.

Trump threatened to slap increasing tariffs on Mexico unless the country stepped up immigration enforcement with the goal of preventing northward movement from Guatemala, Honduras, El Salvador and several other countries with populations that are attempting to flee violence and extreme poverty. Since the June 7 agreement, Mexico has deployed police and newly created national guard units to the southern border with Guatemala, intensified highway checkpoints, and directed border cities to host asylum seekers who make it to the United States and are turned away.

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Mexico’s crackdown aims to deter migrants from attempting to enter the United States, though officials say it is too soon to tell whether it has had any effect on the number of people crossing from Juarez into the southwest Texas city of El Paso. U.S. Border Patrol agents here in the El Paso region have not seen a significant dip in apprehensions since the agreement was signed, said Border Patrol Agent Ramiro Cordero. Agents arrested between 600 and 800 migrants each day in the past week, and migrants still cross the border so often that the sand is dotted with their footprints.

Some migrants said in recent days that the early stages of Mexico’s increased enforcement already has exposed vulnerabilities. Several migrants said in separate interviews that Mexican federal police and other public security forces had demanded bribes of $15 to $20 per person to pass through checkpoints and reach the U.S. border. As buses passed through in recent days, the bribes of hundreds of dollars meant their travel north was essentially unimpeded if Mexican authorities were paid off.

“They said if you want to enter you have to pay,” said Martha Velasquez, 54, of Honduras, who was planning to join her sister, a U.S. citizen, and their mother, a green card holder, in Atlanta. She was returned to Juarez after crossing the U.S. border. “This is extortion.”

Migrants in Juarez said returning asylum seekers to Mexico — if it becomes the inevitable result of trying to cross into the United States — could deter future migrants because conditions there are dangerous and inhospitable. Juarez, once the world’s murder capital, can be a frightening alternative for migrants who had dreamed of reuniting with friends and family in the relative safety of cities across the United States.

‘The migration problem is a coffee problem’

When the ramp-up began Thursday, stunned migrants, some of whom had spent days in border jails, trudged out of Mexico’s immigration office into the sweltering sun. Many had not showered in a week. They had no water, no cellphones, no money and no place to live.

“The American Dream has turned into hell,” said Damarys Perez Carrillo, 38, who said she fled Guatemala after her brother-in-law was murdered. She could not find her 22-year-old nephew Eddy, who was separated from her after they surrendered to Border Patrol in Texas.

“They’re sending us all back,” said Julio Alberto Lopez, a 45-year-old bricklayer from Guatemala who had paid $6,500 to a smuggler for safe passage through Mexico. With his son Abner, 14, he thought he would gain easy entry into the United States, because officials rarely deport families. But within hours, he was returned to Juarez.

“I thought they would give me a chance, with my son,” Lopez said.

'What are we going to do?

Many issues surrounding the anticipated influx remain unresolved: Migrants returned to Mexico are allowed to wait there for their hearings in U.S. courts — a period that sometimes spans months — but they do not have permission to work to support themselves. Many do not have relatives there who can take them in, as they do in the United States. Some are sick and in need of doctors or hospitalization.

“What worries me is that the city and the state, we’re not that prepared,” said the Rev. Javier Calvillo Salazar, who runs the city’s largest migrant shelter, Casa del Migrante. “That could plunge us into a crisis.”

Mexico is under intense pressure to help the U.S. Department of Homeland Security expand MPP, which is also known informally as “Remain in Mexico.” Returns could soar from 250 a day to 1,000 a day along the entire border from California to Texas.

One city that could see more returns is Piedras Negras, a city of 150,000 that sits across the border from Eagle Pass, Tex. The Mexican city has prospered via trade with the United States and has sought to mitigate the migration crush at the border in an effort to appease the U.S. government.

City officials helped block a caravan headed toward the U.S. border and has appointed a steakhouse owner, Hector Menchaca, to run a waitlist that requires migrants to take a number and get in line until the United States invites them in to apply for asylum.

But Menchaca said it would be “catastrophic” for the United States to force those migrants to return to Piedras Negras while they await a decision in the clogged immigration courts.

“What are we going to do on the border with all the migrants, waiting a year for their court date?” Menchaca said. “If they’re illegal, how are they going to work in Piedras Negras? Who’s going to feed them? Where are they going to live?”

'The dream is over'

The U.S. Border Patrol’s El Paso sector, which runs from west Texas into desolate stretches of New Mexico desert, has seen some of the sharpest increases in apprehensions during the migration surge and is likely to see some of the largest increases in returns to Mexico, U.S. officials said.

In Juarez, where violent crime is widespread, migrants must decide whether to return home to their families or test their luck in a nation where they have no connections or support.

Of the 4,500 migrants returned to this city from March to June, municipal officials estimate about 40 percent return to their homelands at their own expense. Sixty percent remain in shelters, rented apartments or with friends.

“That’s where you really see it, the need,” said Rogelio Pinal Castellanos, the human rights director for Juarez’s municipal government. “There are people who say, ‘I’ll die of hunger in Juarez before I’d return to my country,’ because these are people who are really fleeing a critically violent situation. They fear for their lives. And there are those who tell us they’re going home to their country. Or their asylum petition is false.”

Advocates for immigrants caution that migrants with valid cases might flee Juarez because it is dangerous, and they do not have regular access to U.S. lawyers to build their asylum cases.

Ruben Garcia, executive director of Annunciation House, a migrant shelter in El Paso, said expelling asylum seekers is a “wholesale abdication” of the United States’ commitment to refugee protocols.

“This is about ‘keep them out,’ ” he said.

At Valenzuela’s state office this week, some dejected migrants were ready to give up.

“The dream is over,” said Ana Julia Rojas, 46, who officials returned to Juarez with her son Ricardo, 10, dressed in a Captain America T-shirt. She had her brother’s phone number in New York written in ink on her left hand.

Her time in immigration jail soured her on the United States: “I’m going back to Honduras. It’s a poor country, but we’re fighters.”

In a new shelter that opened Friday in a modern white house in Juarez, women shook their heads when Valenzuela asked if they wanted to go home.

One woman’s husband had been shot. Another woman fled an abusive relationship.

But they also did not want to stay in Mexico.

Always another way

Hundreds of miles away along Mexico’s southern border with Guatemala, migrants were continuing to take risks to head north.

In Huixtla, 50 miles north of the Guatemala border, migrants waited to jump atop a northbound cargo train, just west of the nearest checkpoint.

“We were taking buses, but when we saw the checkpoints, we got off and left the highway,” said Kilber Saul, 17, from San Pedro Sula, Honduras.

On Friday morning, they were walking on the train tracks in Huixtla, their only plan to avoid being detained. Mexico’s surge in enforcement has focused on highways, leaving vast stretches of land — and railway — unpatrolled.

“Either we’ll keep walking, or, if the train comes, we’ll ride it,” Saul said.

Advocates said migrants will continue to find their way north until the United States and other nations address the reasons migrants flee their home countries: poverty, hunger, and a lack of security and opportunity.

“Here they put up a wall,” said Pinal Castellanos, Juarez’s human rights director, gesturing to the 18-foot fence that divides Juarez from the United States. “Has this stopped anything? No. People will always find another way, even if it’s risky.”

Kevin Sieff in Huixtla, Mexico, and Nick Miroff in Washington contributed to this report.