A US judge ruled Wednesday that Donald Trump's administration could not immediately expel immigrant minors who arrive alone at the border, a policy the White House said was necessary due to the Covid-19 pandemic. 

Judge Emmet Sullivan of the federal district court in Washington ruled in a preliminary injunction that unaccompanied children arrested at the southern border could not be deported without due process.

The ruling came as part of a lawsuit brought by rights groups on behalf of affected minors.

Citing the pandemic, President Trump's administration in the spring adopted a policy of immediately turning back migrants who arrive illegally at the border and applied the rule to unaccompanied minors, who would usually have access to additional protections.

According to the civil rights organization ACLU, which helped a Guatemalan teenager challenge the rule, 13,000 minors have since been sent back to Mexico or their countries of origin without being able to file asylum requests.

"We are thrilled that the court has enjoined this cruel policy, which has placed thousands of vulnerable refugee children in harm's way," Jamie Crook of the Center for Gender and Refugee Studies, which participated in the lawsuit, said in a statement.

"Today's ruling affirms that the Trump administration cannot use the pandemic as a pretext to flout its legal obligations to children fleeing persecution."

The ruling is the latest blow to the outgoing Trump administration's efforts to curb immigration and asylum-seeking.

On Saturday, a judge rejected the White House's limitations on a program protecting 700,000 so-called "Dreamers," undocumented migrants brought to the United States as children.

President-elect Joe Biden, who defeated Trump in the November 3 polls, had pledged to reinstate the protections granted under a program known as DACA when he takes office on January 20.