The United States is preparing to shelter as many as 20,000 migrant children on four American military bases, a Pentagon spokesman said on Thursday, as federal officials struggled to carry out President Trump’s order to keep immigrant families together after they are apprehended at the border.
The 20,000 beds at bases in Texas and Arkansas would house “unaccompanied alien children,” said a Pentagon spokesman, Lt. Col. Michael Andrews, although other federal agencies provided conflicting explanations about how the shelters would be used and who would be housed there. There were reports of widespread confusion on the border.
It was unclear whether the military housing would also house the parents of children in migrant families that have been detained, and officials at the White House, the Defense Department and the Department of Health and Human Services said on Thursday that they could not provide details.
The Pentagon announcement followed Mr. Trump’s executive order on Wednesday to keep families together after they illegally cross the Mexican border into the United States. The order called for detaining families at the same location.
Democrats questioned the 20,000-bed plan. “Is it even feasible?” Senator Chuck Schumer of New York, the minority leader, asked from the Senate floor.
Advocates for the migrants expressed concern about the prospect of vast settlements of families housed on military bases.
“There’s conflicting instructions being given,” said Michelle Brané, the director of Migrant Rights and Justice at the Women’s Refugee Commission. “It’s another example of this administration making these big, bold policy announcements with no plan for how they are going to implement them.”
“It’s adding to the chaos on the ground,” she said. The tumult echoed the level of confusion among law enforcement agencies at airports after Mr. Trump barred travel for visitors from predominantly Muslim countries a week after he took office last year.
The president’s order this week directed Pentagon officials to provide “any existing facilities available for the housing and care of alien families” and to “construct such facilities if necessary and consistent with law.”
Defense Secretary Jim Mattis sidestepped questions on Wednesday about whether bases might be used as migrant camps, except to say: “We have housed refugees. We have housed people thrown out of their homes by earthquakes and hurricanes.”
On Thursday, the Pentagon did not say which bases would be used for the shelters.
According to estimates, more than 2,300 children under 12 — many of whom are toddlers and infants — are being held in special “tender age” shelters.
A Trump administration spokesman said on Wednesday afternoon that the government would not immediately reunite those children with their parents. But that was contradicted Wednesday night by a more senior official.
On Thursday, Justice Department officials denied a report, apparently issued by officials from another agency, that prosecutions of immigrants traveling with families had been suspended.
Scrambling to adjust and comply with the president’s order, the Border Patrol temporarily stopped referring immigration cases to the Justice Department for prosecution, setting off rumors that it would be halted altogether.
That forced the Justice Department to insist in a statement that “there has been no change to the department’s ‘zero tolerance’ policy to prosecute adults who cross our border illegally instead of claiming asylum at any port of entry at the border.”
Two internal Customs and Border Protection emails supplied to The New York Times showed similar confusion.
In one, sent at 9:54 p.m. Wednesday, Chief Patrol Agent Brian Hastings of the Border Patrol told supervisors that they could continue prosecution referrals for one parent who entered the country illegally if there was another adult migrant present.
But at 4:09 a.m. Thursday, he followed up, saying that agents should “maintain family unity for multi-parent/adult families.”
Last week, federal officials opened a tent city outside El Paso to house up to 360 immigrant teenagers in custody. The temporary shelter site, at a border station in Tornillo, Tex., was still in use on Thursday, and its capacity remains 360, officials said.
In the border city of Del Rio, Tex., American officials continued deporting undocumented immigrants. Luis Alexis Morales, 20, of Veracruz State in eastern Mexico, said he was left in the middle of a bridge that links Del Rio with Ciudad Acuña, Mexico.
“The Border Patrol caught me a week ago crossing the river near Piedras Negras,” Mr. Morales said, referring to a city in northern Mexico across from Eagle Pass, Tex. He said American authorities had held him in jail for the past seven days before deporting him.
On the legal front, Mr. Trump’s lawyers asked Judge Dolly M. Gee of Federal District Court in Los Angeles to modify a 1997 court ruling to allow the indefinite detention of families.
The ruling, known as the Flores settlement, requires that children must be released within 20 days. After that, they are to be sent to a family member or placed in the custody of a licensed, government-sponsored shelter.
The Justice Department said the only way to prevent migrant children from being separated from their parents would be to detain entire families. It seemed to suggest that the practice of separating families could resume if the judge refused to alter the 1997 ruling.
It also echoed a 2016 argument by the Obama administration during a similar migrant surge. The judge and an appeals court denied the requests by the administration’s lawyers.
In 2014, the Obama administration briefly sheltered migrant children at military bases in Texas, California and Oklahoma, establishing emergency housing for a steep increase in unaccompanied minors crossing the border. Around 7,000 children were housed on the bases for about three months until the number of migrants ebbed.
At the time, officials said the government was responding to a rise in the number of unaccompanied children fleeing violence in Central America. The military’s role then was limited to housing the migrants and giving officials from the Department of Health and Human Services access to bases.
It was unclear on Thursday whether the military would play a more central role in Mr. Trump’s plan.
At the White House, the president again lashed out at “extremist, open-border Democrats,” and he again falsely blamed Democrats for the political crisis that continues to roil his administration and was amplified in recent days by images and recordings of young children crying for their parents.
Choosing hard-edge remarks at a cabinet meeting before the House was scheduled to vote on overhauling immigration laws, Mr. Trump asked for Democratic lawmakers’ support on the legislation, even as he said they were causing “tremendous damage and destruction and lives.”
He repeated his false claim that Democrats forced family separations. “They don’t care about the children. They don’t care about the injury. They don’t care about the problems,” Mr. Trump said. “They don’t care about anything.”
In a stream-of-consciousness commentary, the president also attacked Mexico for what he claimed was a failure to help stop illegal immigration into the United States. He said the trek through Mexico from Central America was like a walk through Central Park.
“Mexico is doing nothing for us except taking our money and giving us drugs,” he said.
Mr. Trump said he has directed his administration to “keep illegal immigrant families together and to reunite these previously separated groups.” But he offered no details about how the government intends to reunite the families.
Melania Trump, the first lady, visited a facility in McAllen, Tex., that is holding 55 children who have been separated from their parents.
She took a tour of the Upbring New Hope Children’s Shelter, and in one classroom, she met with a group of children, some of whom spoke to her in English and others in Spanish, which was translated by a teacher.
Officials at the shelter said that the children held there were allowed to communicate with their families by phone twice a week.
“How long are you here? Where are you from?” asked Mrs. Trump, who traveled with Alex M. Azar II, the health and human services secretary. As she left, she said, “Be kind and nice to others, O.K.? Nice to meet you.”
Back in Washington, House lawmakers had been scheduled to vote on Thursday on two broad immigration proposals, even as Mr. Trump’s executive order relieved some of the pressure to act quickly.
The House rejected a hard-line immigration bill in a vote on Thursday afternoon, as had been expected. And Republican leaders delayed the vote on the second bill, which would provide a path to citizenship for young unauthorized immigrants while keeping migrant families together at the border.
That bill, a compromise between moderate and conservative Republicans, had been set for a vote early Thursday evening, but the vote will now take place next week, as it appeared destined to fail as Republicans remained at odds over immigration.
As Mr. Trump reiterated on Thursday his position that congressional action would be the best way to resolve the border crisis, critics of the president announced that they would not wait for such a measure.
A coalition of 10 states filed a lawsuit aimed at making sure that the Trump administration stops separating children from their parents at the border.
“President Trump yesterday signed an empty and meaningless order that claims to take back policies that he put in place himself as a political stunt,” said Xavier Becerra, the California attorney general, who is a plaintiff in the suit. “Meanwhile, these children, their parents and people around the world need answers regarding what comes next.”
The American Civil Liberties Union has already filed a separate lawsuit that demands the government stop separating families and reunite the children who have already been separated with the parents who brought them into the United States.