Watch: White House briefs the press amid controversy over separation of immigrant families

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White House Press Secretary Sarah Sanders is expected to brief reporters on Monday on the administration's controversial "zero-tolerance" immigration policy and the increasing numbers of children being separated from their parents and housed in temporary shelters on the U.S. Mexico border.

The Trump administration has ordered federal prosecutors to pursue criminal charges against all adults who enter the country illegally, regardless of whether those adults are traveling with children. Adults apprehended with their children are being separated, with the minors being placed in the custody of the Department of Health and Human Services.

The Trump administration defended the controversial policy over the weekend, as photographs emerged from detention centers that showed children sleeping on the floor inside wire cages, with only Mylar blankets.

Several Republicans have already come out against the policy, including Sen. Susan Collins of Maine and House Speaker Paul Ryan of Wisconsin, who said on Thursday he opposes separating undocumented immigrant families.

The president went back and forth over the weekend, at times defending the policy and at other times disowning it.

Yet even as Trump held up the policy as evidence of his administration's tough stance on immigration, he simultaneously blamed congressional Democrats for it.

Other conflicting messages about the policy that was formally adopted in May have been coming from across the administration.

Senior White House policy aide Stephen Miller told The New York Times last week that the separation of families was the result of "a simple decision by the administration to have a zero tolerance policy for illegal entry, period," meaning that there would be practically no exceptions made for those with children.

Yet Homeland Security Secretary Kirstjen Nielsen claimed on Sunday that separating families was not the policy of the Trump administration.

Trump himself called the separation of families "so, so sad," during an event Monday.