Customs and Border Protection acting Commissioner John Sanders listens during a news conference where Lindsey Graham, (R-SC)., is proposing legislation to address the crisis at the southern border at the U.S. Capitol on May 15, 2019 in Washington, DC.

Acting Customs and Border Protection Commissioner John Sanders will resign, a CBP official said Tuesday, as the Trump administration faces furor over treatment of migrant children.

He is stepping down amid backlash over conditions at a border patrol facility in Texas. Sanders' departure is effective July 5, the official said.

The New York Times first reported his resignation.

Sanders' decision to step down leaves the White House with yet another vacancy in a key role at a fraught time for U.S. immigration policy. The administration faces bipartisan pressure to improve living conditions for detained children reportedly left with poor nutrition and supervision. President Donald Trump has also threatened mass deportations if he cannot come to an agreement with congressional Democrats on tweaks to immigration laws.

Speaking to reporters Tuesday afternoon, Trump said he did not talk to Sanders about resigning and denied ever speaking to him. But he said he knew "there was going to be a change" at CBP.

Concerns about a facility near El Paso, Texas have also complicated efforts to pass a bill to send emergency aid to address the migrant crisis. After liberal members of the Democratic-held House raised concerns about treatment of migrant children, the party released a revised bill Tuesday that would set health and safety standards for CBP to follow.