President Donald Trump displays an executive order he signed that will end the practice of separating family members who are apprehended while illegally entering the United States on June 20, 2018 in Washington, DC.

The Pentagon has been asked by the federal health department to provide housing on military bases for as many as 20,000 migrant children, a U.S. official said Thursday.

The Department of Health and Human Services has asked the Defense Department if beds for kids caught crossing the border with Mexico illegally could be ready at military bases "as early as July through December 31, 2018," The Washington Post reported, citing a notification to lawmakers.

"How will that work? Is it even feasible?" asked Sen. Charles Schumer of New York, the Senate minority leader, on the Senate floor.

The Post story noted that the Obama administration had used three military bases in 2014 to house around 7,000 children who crossed the border without adult family members.