WASHINGTON: President Donald Trump on Sunday compared people entering the U.S. from Mexico to invaders and said they should be immediately sent back without appearing before a judge.

The American Civil Liberties Union said in response that such a step would be illegal and violate the Constitution that Trump swore to uphold.

“We cannot allow all of these people to invade our Country,” the president said on Twitter as he was being driven to his private golf club in Northern Virginia. “When somebody comes in, we must immediately, with no Judges or Court Cases, bring them back from where they came. Our system is a mockery to good immigration policy and Law and Order.”

“Most children come without parents … Our Immigration policy, laughed at all over the world, is very unfair to all of those people who have gone through the system legally and are waiting on line for years!” he continued. “Immigration must be based on merit - we need people who will help to Make America Great Again!”

“What President Trump has suggested here is both illegal and unconstitutional,” said Omar Jadwat, director of the ACLU’s Immigrants’ Rights Project. “Any official who has sworn an oath to uphold the Constitution and laws should disavow it unequivocally.”

Trump has been criticizing immigration judges for weeks, both exaggerating the number currently hearing cases and saying that hiring more — as some members of Congress have proposed — would be unnecessary.

Meanwhile, the Pentagon is preparing to build temporary camps for immigrants at two military bases, Defense Secretary Jim Mattis said Sunday.

He did not name the two bases, but said the details are being worked out, including how much capacity is needed. The Pentagon had initially talked about four potential bases, but Mattis indicated the number is now two.

The Pentagon last week said it would make space available on military bases for as many as 20,000 unaccompanied migrant children detained after illegally crossing the U.S.-Mexico border. It wasn’t clear Sunday if the housing would be limited to children or if it would also involve families.

The request for temporary shelter — amid a political battle over detained migrants — was made by the Department of Health and Human Services and accepted by the Defense Department.

Republican Rep. Mike McCaul of Texas said on Fox News Sunday that the House needs to pass a wide-ranging immigration bill this week. He said if the House doesn’t act, the nation will see “human tragedy” continue along the border.

McCaul suggested Congress may need to pass a “skinny” immigration bill dealing with family separation if the more wide-ranging version fails.

He said the White House has assured him Trump remains “100 percent” behind House efforts.