WASHINGTON, July 5 (Xinhua) -- U.S. President Donald Trump's administration is using DNA tests to reunite children and their migrant parents after they were separated at the U.S.-Mexico border, the Department of Health and Human Services (HHS) said Thursday.

The agency said compared to verifying documents such as birth certificates, the DNA process is a faster and more accurate method to reunite children aged under 5 with their parents by July 10, and all the children by July 26 -- deadlines set by U.S. Judge Dana Sabraw in San Diego last month.

During a press call with reporters, an HHS official said the method will ensure that children are not handed over to someone falsely claiming to be their parents.

Personnel from HHS, Immigration and Customs Enforcement, and the Department of Homeland Security will collect cheek swab DNA samples from children and parents for the verification.

HHS Secretary Alex Azar didn't give a specific number of children to be reunited with their families under the court order, only saying it would be less than 3,000.

He also expressed frustration with the deadline, describing it as extreme and artificial.

The Trump administration's "zero-tolerance" policy dictates that all immigrants arriving in the U.S. illegally should be detained under federal custody and prosecuted.

Children traveling with their parents were separated from their families, sparking domestic and global outrage. Facing the backlash, Trump signed an executive order on June 20, replacing the family separation with detaining entire families together, including children. The new order ignores the legal time limits on the detention of minority groups.

The administration announced last week that it will now hold families together for longer than 20 days.

According to government figures, between May 5 and June 9, over 2,300 immigrants were separated from their families after illegally crossing the U.S.-Mexico border.