WASHINGTON - The resignation Thursday of the U.S. special envoy to Haiti in protest of what he called "inhumane" deportations of Haitian migrants spotlighted a widening crisis for the Biden administration, as Democratic allies turned on the White House over images of pursuit and squalor that some lawmakers denounced as racist and immoral. 

Daniel Foote's blistering resignation letter accused the administration of conducting a "deeply flawed" policy of returning Haitian migrants to their home country despite the deteriorating political and humanitarian conditions there.

"I will not be associated with the United States' inhumane, counterproductive decision to deport thousands of Haitian refugees and illegal immigrants to Haiti, a country where American officials are confined to secure compounds because of the dangers posed by armed gangs in control of daily life," Foote wrote Secretary of State Antony Blinken.

The move appeared to catch the Biden administration by surprise, although Foote's critique echoed the recent outcry from advocates and lawmakers over the treatment of Haitian migrants massed near Del Rio, Texas. White House press secretary Jen Psaki said Foote "had ample opportunity to raise concerns about migration during his tenure. He never once did so."

In another effort to contain the growing furor, the administration announced it was suspending all horse patrols at the Del Rio migrant camp.

Members of Congress and others have angrily rebuked the Biden administration after images circulated showing U.S. agents on horseback charging at migrants, including family groups, to block their path into the United States.

Rep. Maxine Waters, D-Calif., said the scene of Haitian migrants being chased down by mounted Border Patrol agents "takes us back hundreds of years." Waters said the treatment of Haitians, many of them crammed under a bridge in unsanitary conditions, is "worse than what we witnessed in slavery."

Haiti, the Western Hemisphere's poorest country, is facing an array of crises, including the proliferation of powerful armed gangs, hunger, the spread of the coronavirus and the aftermath of a deadly earthquake in August.

The Biden administration is now preparing to nearly double the number of Haitians being deported to the Caribbean state from Texas, drawing criticism that sending thousands of cash-strapped migrants to the country is unconscionable.

At the same time, officials are releasing many of the Haitian migrants into the United States - and that, too, has attracted criticism, in this case from conservatives and Republicans. The administration has declined to say how many of the migrants are being admitted to the United States.

Foote was named special envoy in July, weeks after the assassination of Haiti's president plunged the country into political turmoil.

On Thursday, Foote complained that his recommendations had been ignored as the administration refused to adjust or drop its policy, continued from the Trump years, of turning away most would-be asylum seekers under a pandemic-related public health order.

The State Department and White House took issue with Foote's critique, standing by the practice of shipping most migrants to Haiti rather than allowing them to stay pending a review of their case for asylum. Officials have said it is the Centers for Disease Control and Prevention that decides whether the public health policy should remain in place.

Some liberal critics have begun comparing President Joe Biden's immigration policies to those imposed by President Donald Trump, whose approach to immigration was reviled by Democrats. Administration officials sharply rejected that message, saying any abuse of migrants under Biden is an aberration that is being corrected as quickly as possible, while under Trump it was official policy.

Psaki said Biden's actions in ordering an investigation triggered by the images and ending horse patrols speak to his own anger at the conditions. The administration hopes to change the deportation policy eventually and explain it more clearly in the interim, she said.

"I think people should take away that it - his actions - make clear how horrible and horrific he thinks these images are, including an investigation, including a change of policy, including conveying clearly that this is not acceptable and he's not going to stand for this in the Biden-Harris administration," Psaki said.

Biden has not personally made any significant public comments about the plight of Haitian migrants. But Psaki rejected any Trump comparisons.

"We could not see it as any more different from the policy of the prior administration, which the president feels - we all feel - was inhumane, immoral, ineffective," Psaki said.

Still, the fact that the administration found itself insisting on its differences from Trump, who made aggressiveness toward immigrants a hallmark of his message, reflected the depth of Biden's plight.

The president's handling of the crisis has drawn sharp condemnations from civil rights leaders, including some who have been Biden allies. Unlike the Central American nations from which many migrants arrived earlier this year, Haiti is a majority-Black country.

"Your commitment to racial equity must extend to the treatment of immigrants," reads a letter sent this week by leaders including NAACP President Derrick Johnson. "As such, we urge you to stop the deportations and immediately grant humanitarian parole to the thousands of Black asylum seekers and process their asylum claims without further delay."

On Monday, the NAACP went further, tweeting a drawing of a white man apparently about to strike a Black enslaved person alongside a photo of a white Border Patrol agent grabbing a Black migrant.