March 16 (UPI) — President Joe Biden’s Homeland Security chief on Tuesday defended the administration’s handling of migrants at the U.S.-Mexico border and its policy of allowing unaccompanied children to stay in the country.

Homeland Security Secretary Alejandro Mayorkas issued a statement Tuesday amid criticism of Biden’s handling of the migrant crisis. There has been a surge this year in unaccompanied children attempting to cross into the United States.

Last weekend, Mayorkas directed the Federal Emergency Management Agency to help process the rise in child migrants. Republicans have criticized Biden’s administration for the surge and some Democrats have complained that it it keeping children in federal custody for too long.

“There is understandably a great deal of attention currently focused on the southwest border,” Mayorkas said in a statement Tuesday.

“The situation at the southwest border is difficult. We are working around the clock to manage it and we will continue to do so. That is our job.”

Mayorkas acknowledged that there has been a surge in migrants at the border under Biden, who has reversed most of former President Donald Trump’s immigration policies, which were widely condemned as cruel and inhumane.

“We are on pace to encounter more individuals on the southwest border than we have in the last 20 years,” he said. “We are expelling most single adults and families. We are not expelling unaccompanied children.”

“We are securing our border,” he added.

Mayorkas said the majority of migrants crossing the border are single adults who are being sent back under federal COVID-19 safety protocols. Families from Mexico, Honduras, El Salvador and Guatemala are also being sent back to Mexico, he said.

The unaccompanied children, he said, cannot be sent back.

“We are encountering six- and seven-year-old children, for example, arriving at our border without an adult,” he said. “They are vulnerable children and we have ended the prior [Trump] administration’s practice of expelling them.”

“The children then go through immigration proceedings where they are able to present a claim for relief under the law,” he added.

Mayorkas noted that similar migrant surges were seen in 2019 and 2014 and said the numbers have been steadily increasing since last April.

Part of the problem that’s added to rising migration, Mayorkas added, is violence in Mexico and Central America, the coronavirus pandemic and two hurricanes that hit Guatemala during the 2020 hurricane season.

Also part of the problem, he said, was the Trump administration’s hard line anti-immigration policy.

“The prior administration completely dismantled the asylum system,” he said. “The system was gutted, facilities were closed, and they cruelly expelled young children into the hands of traffickers. We have had to rebuild the entire system, including the policies and procedures required to administer the asylum laws that Congress passed long ago.”

“As difficult as the border situation is now, we are addressing it,” he added. “We have acted and we have made progress. We have no illusions about how hard it is, and we know it will take time. We will get it done.”