The United States is facing the biggest surge of migrants at its southwestern border in two decades, the Department of Homeland Security said on Tuesday.

Border control officers are currently grappling with increasing numbers of children who are trying to cross into the country from Mexico by themselves.

The number of attempted border crossings by people from Mexico and neighboring countries has steadily increased over the last year, US Homeland Security Secretary Alejandro Mayorkas said in a statement. The majority of single adults and families are being turned away, he said.

DHS: COVID concerns add to the surge

Decades of poverty, violence and corruption in Mexico, Guatemala, Honduras and El Salvador have led to millions of people trying to flee to the US.

And conditions in the Latin American countries have continued to deteriorate. Two recent hurricanes have made living conditions even worse, while the coronavirus pandemic complicated the border situation further still, Mayorkas said.

"We are on pace to encounter more individuals on the southwest border than we have in the last 20 years," he said.

US border agents carried out 100,441 apprehensions or expulsions of migrants at the border with Mexico in February alone, the White House's Customs and Border Protection said last week, the highest monthly total in two years.

Children traveling alone

Single adults make up the majority of people who are being expelled, Mayorkas said. Children who arrive alone, some as young as six years old, are not being turned back.

The US government is creating a joint processing center to transfer the children promptly into the custody of the Department of Health and Human Services (HHS) and is trying to find additional shelters for them, Mayorkas added.

President Joe Biden's administration has been struggling to speed up the processing of hundreds of youths under 18 who are crossing the southern border alone every day.

"We will have, I believe by the next month, enough of those beds to take care of these children who have no place to go, but they need to be taken care of," Biden said in an interview with ABC News on Tuesday.

Republicans: Biden's immigration policies to blame

Republicans in Congress accused the president of causing the border surge by promising to roll back some of his predecessor's hardline policies on immigration.

"It didn't have to happen," House of Representatives Republican leader Kevin McCarthy said at an El Paso border facility on Monday. "This crisis is created by the presidential policies of this new administration."

The mounting criticism saw Biden tell potential migrants on Tuesday: "Don't come over ... Don't leave your town or city or community."

jsi/msh (Reuters, AP, AFP)