President Biden said Thursday that he has appointed Vice President Kamala Harris to lead his administration’s efforts to address a record surge in migrants, including unaccompanied minors, that has strained capacity at immigration facilities at the southern border in recent weeks.

Harris will serve as the administration’s diplomatic liaison in talks with Mexico and the "Northern Triangle" nations of Honduras, Guatemala and El Salvador on how best to address the root causes of the migrant surge, according to Biden. The president said his administration would also reinstitute funding to aid development and immigration enforcement in border nations.

"This new surge we’re dealing with now started with the last administration, but it’s our responsibility to deal with it humanely and to stop what’s happening," Biden said. "This increase has been consequential, but the vice president’s agreed – among the multiple other things I have her leading and I appreciate it – agreed to lead our diplomatic effort and work with those nations to accept the returnees and enhance migration enforcement at their borders."

Biden noted that he received a similar assignment while serving as vice president in the Obama administration. The president identified several factors, including gang violence and natural disasters, that he said prompted migrants to flee their homes.

The president said Harris’ experience as the former attorney general of California made her uniquely qualified to lead the administration’s efforts. But Harris’ appointment places the former presidential candidate at the center of a politically fraught debate over how best to handle the border crisis.

GOP lawmakers say Biden administration’s decision to reverse Trump-era immigration policies prompted the latest surge in migrants. The White House has argued that Biden inherited a chaotic situation and is working to stabilize the border.

Earlier this week, the Biden administration drew criticism from Democrats after photos emerged of cramped conditions at an overflow facility in Texas.

In her first remarks on the role, Harris said there was "no question this is a challenging situation."

"As the president has said, there are many factors that lead [migrants] to leave these countries," Harris said. "While we are clear that people should not come to the border now, we also understand that we will enforce the law and that we also, because we can chew gum and walk at the same time, must address the root causes that cause people to make the trek."

More than 15,000 unaccompanied migrant minors are in custody at federal facilities, according to recent reports. U.S. Customs and Border Protection reported encounters with more than 100,000 migrants in February alone.

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Lawmakers from both parties have either visited border facilities or scheduled trips amid the mounting crisis. A group of White House officials were set to tour a Texas facility used to house unaccompanied minors on Wednesday.

Neither Biden nor Harris has visited the southern border since taking office, though the president recently said that he would do so "at some point."

The Associated Press contributed to this report.