From right: Former President Barack Obama, former USA first lady Michelle Obama, former President George W. Bush and former first lady Laura Bush attend the dedication of the Smithsonian's National Museum of African American History and Culture in Washington, D.C., on September 24, 2016. I appreciate the need to enforce and protect our worldwide boundaries, but this zero-tolerance policy is cruel. "It is immoral. And it breaks my heart", Bush writes.
Laura Bush compared the zero-tolerance policy to the internment of Japanese-Americans during World War II, which she called "one of the most shameful episodes in US history". But she said the images of children getting taken from their parents broke her heart.
After touring a converted Walmart supermarket that is now housing about 1,500 immigrant children, Mr Merkley said "hurting kids to get legislative leverage is unacceptable".
The former first lady published an opinion article in the Washington Post Sunday. She reported that while there were beds, toys, crayons, a playground and diaper changes, the people working at the shelter had been instructed not to pick up or touch the children to comfort them.
Donald Trump has previously blamed a law that "Deomcrats gave us" for the detentions, but it remains unclear which law he means. The current policy stems from the Trump administration's "zero tolerance" toward people crossing the border illegally.
Over the course of a six-week period, almost 2,000 children have been separated from their parents at the border due to strict immigration policies.
Next week, Congress is set to vote on two immigration proposals - the conservative McCaul-Goodlatte bill, and a more moderate House GOP bill.
Miller, who is Jewish, argued in White House meetings that the new policy would deter illegal immigration.
"Nobody likes" breaking up families and "seeing babies ripped from their mothers' arms", Ms Conway said.
The border processing center is the first place that detained immigrants go after they are arrested, but the stay is only temporary, CBP officials said.