The acting commissioner of the U.S. Customs and Border Protection (CBP) agency, John Sanders, is resigning and will leave his post on July 5, the agency said on Tuesday, a move that coincides with an outcry over the treatment of detained migrant children.
The relocation of 250 migrant children from an overcrowded Texas border patrol station, where they were held for weeks in squalid conditions without adequate food and water, has stepped up criticism from immigration activists and Democrats of Republican President Donald Trump's hardline immigration policies.
The New York Times first reported that Sanders was resigning. Sanders has led the agency since April, when Trump reshuffled the management of U.S. immigration agencies under the Department of Homeland Security.
Before taking over CBP, he was the agency's chief operating officer and had also been the Transportation Security Administration's chief technology officer.
Dealing with a surge of migrants at the U.S.-Mexico border has been a priority for Trump but the president has proven unable to push most of his goals through Congress.
On Tuesday, U.S. House Democrats said they plan to approve $4.5 billion in emergency funding to address the crisis caused by the migrant surge, but the measure has drawn a veto threat from Trump.
"This week we have to solve the humanitarian crisis," House of Representatives Democratic Caucus Chairman Hakeem Jeffries told reporters, predicting that the funding package would pass the House with a "strong Democratic vote."
But lawmakers were also rushing to add language before the vote to mandate better health and nutrition standards at border facilities.
The changes were being made after some liberal Democrats expressed alarm that not enough was being done to improve conditions at the border, where the number of migrants apprehended surged in May to the highest level since 2006.