Trump has defended his policies that separate migrant children from parents.
An unapologetic US president Donald Trump has defended his administration's border-protection policies in the face of rising national outrage over the forced separation of migrant children from their parents.
Calling for tough action against illegal immigration, Mr Trump declared the US "will not be a migrant camp" on his watch.
Images of children held in fenced cages fuelled a growing chorus of condemnation from both political parties, former first ladies and national evangelical leaders.
The children are being held separately from parents who are being prosecuted under the administration's "zero-tolerance" policy for illegal border crossings.
"I say it's very strongly the Democrats' fault," Mr Trump said on Monday as his administration rejected criticism that the policy has resulted in inhuman and immoral conditions.
Mr Trump pointed to more lenient policies under past administrations that had not charged all migrants who had crossed illegally.
"We will not apologise for the job we do or for the job law enforcement does, for doing the job that the American people expect us to do," homeland security secretary Kirstjen Nielsen said in an appearance before the National Sheriffs' Association in New Orleans.
"Illegal actions have and must have consequences. No more free passes, no more get-out-of-jail-free cards."
Nearly 2,000 children were separated from their families over a six-week period in April and May after attorney general Jeff Sessions announced the new "zero-tolerance" policy that refers all cases of illegal entry for criminal prosecution.
Prior procedure had limited prosecution for many family entrants, in part because regulations prohibit detaining children with their parents since the children are not charged with a crime and the parents are.
The policy change was meant to deter unlawful crossings - and Mr Sessions issued a warning last month to those entering the US illegally that their children "inevitably for a period of time might be in different conditions".
The present holding areas have drawn widespread attention after journalists gained access to one site on Sunday.
At a McAllen, Texas, detention centre hundreds of immigrant children wait in a series of cages created by metal fencing. One cage had 20 children inside. Scattered about are bottles of water, bags of chips and large foil sheets intended to serve as blankets.
Audio of sobbing children calling out for their parents dominated the discussion on Monday.
"Papa! Papa!" one child is heard weeping in an audio file that was first reported by the non-profit ProPublica and later provided to The Associated Press.
Administration officials said they do not like the family separations either – calling it the result of legal loopholes – but insist migrants who arrive illegally simply will not be released or loosely kept track of.
Mr Sessions, on Monday, echoed the administration's defence of the zero-tolerance policy, and called on Congress to act.
"We do not want to separate parents from their children," he said. "If we build the wall, if we pass legislation to end the lawlessness, we won't face these terrible choices."
Mindful of the national outcry, politicians in both parties rushed to devise a targeted legislative fix.
Republican senators, including Lindsey Graham of South Carolina, Jeff Flake of Arizona and Susan Collins of Maine, said they were considering legislation that would keep migrant families together; provide additional judges so detained families would face shorter waiting periods; and provide facilities for the families to stay.
Mr Graham said he talked to about 40 senators, including Democrats, but not Senate Majority Leader Mitch McConnell. "It's a concept it seems everybody is jumping on board," he said.
California Senator Dianne Feinstein said she had the backing of the Democratic caucus for a bill would that prohibit the separation of migrant children from their parents, with exceptions for findings of child abuse or trafficking.
But the White House signalled it would oppose any narrow fix aimed solely at addressing the plight of children separated from their parents under the immigration crackdown.
Press secretary Sarah Sanders said Mr Trump's priorities, like funding a border wall and tightening immigration laws, must also be fulfilled as part of any legislation.
"We want to fix the whole thing," she said.
"We don't want to tinker with just part of it."