But the president said the "zero tolerance" policy, under which every adult caught crossing the border illegally will be detained and prosecuted, will continue.

"We're signing an executive order. I consider it to be a very important executive order. It's about keeping families together, while at the same time being sure we have a very powerful, very strong border," Trump said.

Heart-rending images and sounds of wailing children separated from their guardians have led to a firestorm of opposition to the Trump administration's crackdown on illegal immigration.

Pressure also grew Tuesday night after Trump administration officials have reportedly been sending babies and other young children forcibly separated from their parents at US-Mexico border to at least three "tender age" shelters in South Texas.

According to government figures, more than 2,300 minors separated from their families after illegally crossing the US southern border with Mexico from May 5 through June 9.

The president had claimed that the crisis of family separations could not be resolved by an executive order and insisted that previous administrations, Democrats and Congress were to blame for the situation.