UPDATE 1-U.S. defends response to child migrant surge at southwest border

Adds details, background

WASHINGTON, March 16 (Reuters) - Homeland Security Secretary Alejandro Mayorkas defended the U.S. response to a surge of unaccompanied minors at the southwest border on Tuesday, saying the region was on track to see more people trying to enter than any time in the last 20 years.

Mayorkas said the government is creating a joint processing center to transfer the children, as young as six, to the custody of the Department of Health and Human Services and is trying to find additional shelters for them.

"The situation we are currently facing at the southwest border is a difficult one. We are tackling it," he said in a statement.

The administration of President Joe Biden has been racing to speed up the processing of hundreds of unaccompanied children who are crossing the southern border every day.

Officials have warned "the border is not open" and said they are sending back adults and families who have tried to cross the border illegally since Biden took office promising to reverse some of predecessor Donald Trump's hardline policies.

Nearly 4,300 unaccompanied children were being held by border patrol officials as of Sunday, according to an agency official who requested anonymity to discuss the matter. By law, the children should be transferred out of Customs and Border Protection facilities to HHS-run shelters within 72 hours. nL1N2LD27F

"The Border Patrol facilities have become crowded with children and the 72-hour timeframe for the transfer of children from the Border Patrol to HHS is not always met," Mayorkas acknowledged. HHS also has not had the capacity to take in the number of children, he said.

(Reporting by Doina Chiacu and Susan Heavey; Editing by Andrew Heavens and Nick Zieminski)

((doina.chiacu@thomsonreuters.com; 202-898-8322;))