WASHINGTON -- The US special envoy to Haiti resigned in protest on Thursday at the Biden administration for deporting hundreds of migrants back to the crisis-engulfed Caribbean nation from a camp on the US-Mexican border in recent days.

Daniel Foote wrote Secretary of State Antony Blinken that he was stepping down immediately “with deep disappointment and apologies to those seeking crucial changes.”

“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 danger posed by armed gangs to daily life,” he wrote.

“Our policy approach to Haiti remains deeply flawed, and my policy recommendations have been ignored and dismissed, when not edited to project a narrative different from my own.”

Foote, a career diplomat named to his post in July, said conditions in Haiti were so bad that US officials were confined to secure compounds. He said the "collapsed state" was unable to support the infusion of returning migrants.

The United States has returned 1,401 migrants from the camp to Haiti and taken another 3,206 people into custody, the Department of Homeland Security said on Wednesday.

Haiti, the poorest nation in the Western Hemisphere, has gone through profound instability in recent weeks, including a presidential assassination, gang violence and a major earthquake.

Foote’s sudden departure leaves a void in U.S. policy toward Haiti — U.S. Ambassador Michele Sison is expected to depart soon after being nominated to serve in another State Department’s post — and adds another critical voice to the administration’s response to Haitians camped on the Texas border.

Criticism has been fueled by images that went viral this week of Border Patrol agents on horseback using aggressive tactics against the migrants. Democrats and many pro-immigration groups say efforts to expel thousands of Haitians without a chance to seek asylum violates American principles and their anger has been fueled

The migrant camp has shrunk considerably since surpassing more than 14,000 people on Saturday – many of them expelled and many released in the U.S. with notices to report to immigration authorities.

Filippo Grandi, the head of the U.N refugee agency, warned that this week the U.S. expulsions to Haiti might violate international law.

Foote submitted his resignation to Blinken on Wednesday, a State Department spokesperson said, adding that Washington was committed to the long-term well being of Haiti, as well as offering immediate help to returning migrants.

The resignation follows growing pressure on the administration of U.S. President Joe Biden from the United Nations and his fellow Democrats over the treatment of Haitians in a impromptu migrant camp in Texas near the Mexican border.

Biden's handling of what Republicans portray as a crisis at the border -- including record numbers of migrant detentions this year -- has led to growing disillusionment from advocates who hoped for an end to deterrent measures brought in by his predecessor Donald Trump.

A State Department spokesman gave no indication of a change in policy, saying the United States is working with the International Organization on Migration to ensure that returning Haitian migrants are met at the airport and provided with immediate assistance.

"We are working to identify ways to provide more comprehensive assistance going forward," the spokesperson said.

As well as the Haitians, the United States frequently deports Central American and other migrants caught crossing the border.

Foote's decision to leave was interpreted and welcomed by rights groups as a stern criticism of the administration's immigration strategy.

"A big bold move. And a big deal," said William O'Neill, a lawyer specializing in humanitarian, human rights and refugee law. "He will be missed."

Wade McMullen, an attorney with the Robert F. Kennedy Human Rights organization, said several hundred people, mostly pregnant women and parents with children, had been released in Del Rio, Texas, over the past several days. -- Agencies