The top White House official leading efforts to address the migrant crisis at the U.S.-Mexico border will leave her post at the end of April, the White House announced Friday, stepping down as the administration continues struggling to cope with an influx of unaccompanied minors.

Roberta S. Jacobson, a former ambassador to Mexico and career State Department official, had been tasked with coordinating the Biden administration’s efforts, a broad and daunting task that led some to call her Biden’s “border czar.”

Vice President Harris was recently assigned to oversee the part of Jacobson’s portfolio involving diplomatic outreach to the Central American nations that are home to most of the migrants.

It’s not clear whether that was a factor in Jacobson’s departure, but both U.S. and Latin American officials said that Jacobson had always planned to stay only briefly.

Jacobson, in an interview, expressed dismay over media reports that she had acted in response to Biden’s giving Harris the lead role on the overall border and regional issue.

“I always was only going to stay 100 days,” she said, and had filled a need during the early days when there were relatively few confirmed officials.

“They knew they were going to have to talk to the Mexican government early,” as first-day executive orders on immigration were implemented, and there “were not other people appointed at other agencies,” including the secretary of state, Jacobson said.

Now, she added, “I think it is in quite good shape in terms of policy outlines.”

Jacobson also was a senior member of the Biden transition team focusing on the State Department, and she was working border issues starting right after the election.

National security adviser Jake Sullivan said in a statement that Jacobson’s tenure was long planned to cover only the administration’s first 100 days. He thanked her for “an invaluable contribution to the Biden-Harris Administration and to the United States.”

Sullivan credited Jacobson with “having shaped our relationship with Mexico as an equal partner, having launched our renewed efforts with the Northern Triangle nations of El Salvador, Guatemala, and Honduras, and having underscored this Administration’s commitment to re-energizing the U.S. immigration system.”

Still, her departure is striking, coming as the Biden administration is struggling to address a surge of would-be migrants to the border, drawn in part by President Biden’s more lenient immigration policy, and amid heavy Republican criticism of the administration’s approach. The administration has wrestled in particular with how to handle a large number of unaccompanied children who are showing up at the border.

The number of unaccompanied minors crossing into the United States began rising last fall, as former president Donald Trump’s tenure was coming to a close. They soared after Biden took office and his administration announced that it would not use a Trump-era public health order to return the unaccompanied teens and children to their home countries.

Last month, border authorities took 18,890 minors into custody, up from 5,858 in January.

March was the busiest month along the U.S.-Mexico border in nearly two decades, and U.S. authorities took 172,331 migrants into custody, according to U.S. Customs and Border Protection statistics released Thursday that provide a stark measure of the challenges facing the Biden administration.

White House press secretary Jen Psaki was asked earlier Friday whether the rising numbers might cause the administration to again evict and turn back children under Trump’s public health order.

“The reason for accepting these children is that we feel it is not the humane step to send these kids back on their treacherous journey,” Psaki said. “Our focus is on addressing the needs, opening up shelters, ensuring there is access to health and educational resources, expediting processing at the border. And those are the steps we feel that are most effective from a policy standpoint.”

Jacobson spoke to reporters at the White House last month and acknowledged the significant challenge of addressing the flow of families and unaccompanied children.

“President Biden has made clear from day one that he wants to change our immigration system,” she said then. “Doing so means truly building back better, because we can’t just undo four years of the previous administration’s actions overnight.”

She and other Biden officials have sharply blamed the Trump administration for its hostility to migrants, saying they damaged the system in ways that take time to fix.

“Those actions didn’t just neglect our immigration system; they intentionally made it worse,” Jacobson said. “When you add a pandemic to that, it’s clear it will take significant time to overcome.”

She said then “the border is not open” and spoke at length in Spanish to urge would-be migrants not to make a dangerous trip with little likelihood of successful entry.

But Republican and some Democratic critics say Biden’s own policies have created the problem, and GOP lawmakers have held events at the border to make their point.

Jacobson came out of retirement to join the Biden administration as a “border coordinator” who could leverage her experience and extensive contacts in Mexico.

As border crossings jumped in the weeks after Biden’s inauguration, Jacobson took the lead in negotiations with Mexico and in the U.S. efforts to get the government of Andrés Manuel López Obrador to tighten immigration enforcement.

Last month Mexican authorities deployed more national guard troops and other security forces along the country’s southern border with Guatemala, the result of a negotiation in which the Biden administration agreed to send millions of surplus coronavirus vaccines made by AstraZeneca. Jacobson played a lead role in the talks, which officials in both countries insisted did not amount to a quid pro quo.

The number of migrants taken into custody by U.S. border agents is the highest level in nearly 20 years, including record numbers of teenagers and children arriving without parents. The Biden administration has responded by adding thousands of emergency shelter beds for the minors, while pledging to redouble efforts to address the “root causes” driving Central Americans to head north.

Jacobson issued one of the strongest statements by any Biden official last month, when asked about the administration’s message to asylum seekers.

“The message isn’t, ‘Don’t come now.’ It’s, ‘Don’t come in this way, ever,’ ” she told Reuters in an interview. “The way to come to the United States is through legal pathways.”

Biden has pledged to try to stem the flow of migrants at the source by helping create stability and economic opportunity in Central America and Mexico. That longer-term effort is now Harris’s remit, and she distinguishes her role from that of Jacobson and other officials dealing with the more immediate humanitarian and logistical crises facing migrants who have made their way to the border.

Earl Anthony Wayne, who served as U.S. ambassador to Mexico until 2017, called Jacobson “one of the United States’ most experienced experts on Mexico.”

“She has a range of contacts there and a deep understanding of Mexican politics,” said Wayne. “Those are valuable assets to have at this time, so it will be important for the administration to find someone who can bring the expertise and skills that she has demonstrated over her years of service.”

The Biden administration appears to be spending at least $60 million per week to care for the more than 16,000 migrant teenagers and children in shelters operated by the Department of Health and Human Services, The Washington Post reported Thursday.

Those costs are expected to rise significantly over the coming months, according to an analysis of government data obtained by The Post.

With a record number of unaccompanied minors arriving at the border in the past several weeks, HHS quickly filled the 7,700 available beds in its network of permanent shelters, and the administration has raced to set up some 16,000 temporary beds at military bases and other facilities.