In one tweet, he wrote, "We can not allow all of these people to invade our Country".
He said, "When somebody comes in, we must immediately, with no Judges or Court Cases, bring them back from where they came".
It was unclear if Trump was advocating an expansion of the current law that allows expedited removal of illegal immigrants at the USA border, a policy his administration has embraced since he took office. Trump also suggested last week that he opposed adding judges because many of them could be corrupt.
President Trump tweeted on Sunday that the USA immigration system is "laughed at all over the world" and is "very unfair" to individuals using legal avenues to gain entry. Earlier, Trump leaned once again on Democratic lawmakers to "fix" immigration laws and prevent people attempting to "break into" the US.
And Trump faced backlash for his administration's policy separating immigrant children and parents at the border before he ended the policy last week. More than 2,300 children were separated from the adults they crossed the border with, provoking outrage around the world and producing a public relations nightmare for the administration. Don't RESIST. We are doing a far better job than Bush and Obama, but we need strength and security at the Border!
"The president of the United States has just forcefully proposed the end of political asylum and no due process for migrants", Sherrilyn Ifill, president of the NAACP Legal Defense Fund, wrote on Twitter.
Brazil beat Costa Rica 2-0 in thriller; edge towards last 16
As he hid his face inside his blue Brazil shirt, he had the look of a man who wondered if he had squandered his best opportunity. And Coutinho scored in the first minute of stoppage time to give Brazil a 1-0 lead over Costa Rica in this World Cup clash.
"What President Trump has suggested here is both illegal and unconstitutional", said Omar Jadwat, director of the ACLU's Immigrants' Rights Project.
The president buckled to the pressure on Wednesday, issuing an executive order that ended the separations.
Immigrant rights activists have condemned the proposal, warning that it could violate due process requirements.
Still, Trump has rejected calls for additional immigration judges at the border, instead calling for strong security and a border wall. That required children to be separated from parents because they are not legally allowed to be kept in detention for more than 20 days.
Families in detainment wait until their case is brought before an immigration judge.
"What President Trump has suggested here is both illegal and unconstitutional". House Speaker Paul Ryan (R., Wis.) last week declined to comment on the next steps should a broad immigration bill fail to clear the House, although there is widespread support among Republicans for a narrow measure to provide a legal basis for keeping families together.