WASHINGTON (REUTERS) - The Trump administration will soon begin fingerprinting parents claiming custody of children who entered the United States illegally without an adult relative, officials said on Tuesday (May 29), prompting criticism that children may be abandoned by those who fear being identified and deported.

Currently, most parents are not required to be fingerprinted to get custody of their children.

US laws and legal precedent limit the time juveniles can be detained, so those caught crossing the border alone are often released to adult sponsors in the United States.

The children are then expected to show up to immigration court to fight their deportation cases.

"We're going to more thoroughly vet sponsors," said Mr Steven Wagner, acting assistant secretary of the Department of Health and Human Services' (HHS) Administration for Children and Families, in a telephone briefing with reporters.

"With DHS' cooperation, we will conduct a fingerprint-based background check on every sponsor."

HHS is ultimately responsible for finding housing for migrant children, and the Department of Homeland Security (DHS) enforces immigration policy.

Under a new memorandum, DHS would help HHS fingerprint every individual claiming custody of a child, senior officials said.

A DHS official who declined to be named said they expect implementation in a few weeks.

Immigrant advocates said the new policy would discourage parents from claiming their children.

"This policy will undoubtedly make it more likely that qualified sponsors will hide in the shadows, leaving vulnerable young children to languish in immigration jail," said Mr Rich Leimsider, executive director of the Safe Passage Project, which represents immigrant children in New York, in an e-mail to Reuters.

Mr Wagner, during the briefing, dismissed such concerns.

"If somebody is unwilling to claim their child from custody because they're concerned about their own immigration status, I think that de facto calls into question whether they're an adequate sponsor and whether we should be releasing the child to that person," Mr Wagner said.

In March and April, more than 50,000 people were detained per month trying to cross the south-west border illegally, levels similar to those during the administration of Mr Barack Obama, according to US government figures.

During those two months, a total of about 8,400 unaccompanied minors were caught on the south-west border.

Soon after President Donald Trump's inauguration in January 2017, border crossings briefly dropped to record lows before creeping back up again at the end of last year. The increase has frustrated Mr Trump, who has repeatedly called for more action.

A controversy erupted after Mr Wagner testified in April before a Senate committee that the agency in 2016 conducted a limited"safety and well-being" call to around 7,600 children that had been in its care, but was unable to locate around 1,500 children and their sponsors.

On Tuesday, Mr Wagner said many children are with people who are in the country illegally and that "there's no reason to believe that anything has happened to those kids".

Currently, all sponsors of unaccompanied children undergo an interview and a background check, and non-parental sponsors undergo fingerprint checks of a Federal Bureau of Investigation database.

In special cases, such as when there is a "documented risk" to the safety of the child, parents will undergo fingerprint checks as well, according to the HHS website.

Background checks and interviews may turn up immigration information, which is entered into an HHS web portal, but immigration status is not used to disqualify sponsors.

HHS cannot "deny placement" based on immigration status, Mr Wagner said.

From January 2014 to April 2015, 60 per cent of unaccompanied children from El Salvador, Guatemala and Honduras were released to a parent, about a third were released to other relatives, 8 per cent to family friends and less than 1 per cent was released to unrelated sponsors, according to a 2018 Government Accountability Office report.

During the Obama administration, officials at US Immigration and Customs Enforcement proposed that anyone claiming custody of unaccompanied alien children be fingerprinted.

HHS officials at the time pushed back, arguing that it would delay family reunions and infringe upon the parent-child relationship.