Washington - American authorities are planning a major operation to round up and expel migrant families living in the country illegally, US media reported on Thursday.
The Department of Homeland Security could not confirm - but did not dispute - the anonymously-sourced reports in the Washington Post, Wall Street Journal and several other outlets.
And spokesperson Gillian Christensen told AFP that Homeland Security Secretary Jeh Johnson "has consistently said, our border is not open to illegal immigration".
"If individuals come here illegally, do not qualify for asylum or other relief and have final orders of removal, they will be sent back consistent with our laws and our values," she said, citing Johnson.
According to the Washington Post, the number of mainly Mexican and Central American families targeted in the planned crackdown will be "in the hundreds and possibly greater".
These would be migrants whose applications for asylum have been refused and are subject to a court order to leave.
Any such operation would be controversial.
Refugee rights activists argue that the families are fleeing corruption, violent crime and drought - the Pacific basin is beset by a severe El Nino weather pattern - in their homelands.
Over the course of the 2015 fiscal year, arrests of non-documented migrants crossing the US border from Mexico dropped by a third to the second lowest level since 1972.
The number of children crossing without their relatives - which surged in 2014 amid a deadly crime wave in some parts of Central America - was also down over the period.
But the number of minors and of families crossing began to increase again sharply towards the end of 2015, alarming the Department of Homeland Security.
According to US Customs and Border Protection, arrests of members of "family units" on the US southwest border in October and November - the first two months of the 2016 fiscal year - were up 173% over the same period last year.
Arrests of unaccompanied minors are up 106%.
Immigration is one of the most hotly debated topics in the 2016 US presidential campaign, with Republican hopefuls including Donald Trump vying with each other for who can promise the toughest stance.
President Barack Obama's opponents - some of whom like Trump have demanded a massive border wall be built - will argue that the reported DHS plan is a stop-gap to disguise a broken system.