Governor Kate Brown of the U.S. west state of Oregon Thursday strongly criticized U.S. President Donald Trump's administration for its controversial family separation policy that ripped immigrant children from their parents.

"This week, we have seen immigrant children taken from their families, and kept in warehouses, cages, and tents along the border. It's appalling that these children are being used as political pawns by the White House," Brown said in an address at the annual gathering of the National Association of Attorneys General.

Facing domestic and international backlash, Trump signed an executive order Wednesday to end the administration's controversial practice of separating migrant children from parents crossing the U.S. border illegally.

The move came as the practice, which resulted from the Trump administration's "zero tolerance" policy against illegal immigration, has caused outrage and sharp criticism from both home and abroad in recent days.

Critics have denounced Trump's immigration policy as cruel and inhumane, as nearly 2,000 children were forcibly separated from their parents during a sweeping campaign by the Trump administration to crack down on illegal immigration in April and May.

In California, the Department of Justice slammed Washington's practice of forcibly ripping migrant children from their parents at the U.S. border as a "cruel and unlawful policy ... without any legitimate justification."

"Children belong with their families, not alone and fearful in metal cages," California Attorney General Xavier Becerra said earlier Thursday.

He said California is joining a coalition of 10 U.S. states in filing a lawsuit against the Trump administration's family separation policy.

"We are filing this lawsuit because ripping children from their parents is unlawful, wrong and heartless," he said.

The lawsuit, led by Washington Attorney General Bob Ferguson, will allege that the Trump administration's family separation policy violates the fundamental due process rights of parents to be together with their children, as well as other constitutional and statutory claims.