NEW YORK: A testy exchange between Donald Trump and Joe Biden in Thursday’s TV debate has renewed focus on the unknown whereabouts of parents of 545 migrant children, separated from their families under US border policy.

President Trump appealed to his right-wing base by defending the “zero-tolerance” policy that prosecuted immigrants, who crossed into the US illegally, separating over 5,000 children from their parents in 2017 and 2018.