President Trump on Friday continued his crackdown on illegal immigration, signing sweeping new orders that tighten the country’s refugee and visa policies –suspending almost all refugee admissions for four months and indefinitely barring entry for some Syrians.

Trump signed the executive action at the Pentagon, where he met with the joint chiefs of staff and participated in the swearing-in ceremony for Defense Secretary James Mattis.

"We don’t want them here." — President Trump

Trump said the new measure was intended “to keep radical Islamic terrorists out of the United States of America.”

“We don’t want them here,” Trump said.

The executive order also suspends visa entry into the U.S. from seven countries that have predominately Muslim populations. They include: Syria, Iran, Iraq, Somalia, Libya, Sudan and Yemen.

The order also creates an “extreme vetting” process for any and all immigrants and visitors to the U.S.

House Chairman Rep. Michael McCaul, R-Texas, told Fox News, “It’s a safer day for America.”

American Civil Liberties Union Executive Director Anthony Romero blasted Trump's plan as unconstitutional.

“‘Extreme vetting’ is just a euphemism for discriminating against Muslims," Romero said in a statement issued moments after the signing. "Identifying specific countries with Muslim majorities and carving out exceptions for minority religions flies in the face of the constitutional principle that bans the government from either favoring or discriminating against particular religions."

Trump defended the executive order during an interview with Fox News’ Sean Hannity.

"Right now, the FBI has over 1,000 [terrorism] investigations going on … and these are people that we let in," Trump said from the White House Thursday. "We don’t need this. Some people have come in with evil intentions. Most haven’t, I guess, but we can’t take chances."

Trump added that the U.S. has taken in tens of thousands of people.

“We know nothing about them,” he said. “They can say they vetted them. They didn’t vet them, they have no papers. How can you vet somebody when you don’t know anything about them and they have no papers?”

Civil rights and refugee advocates around the world have sounded the alarm over Trump’s executive order after a draft copy was leaked late Wednesday.

“These actions taken by Donald Trump are tantamount to a Muslim ban,” Abed A. Ayoub, the legal and policy director for the American-Arab Anti-Discrimination Committee. “This is the Muslim ban that was promised by him on the campaign trail.”

As president, Trump has the authority to set how many refugees are allowed in annually. He can also choose to suspend the program altogether. Following the Sept. 11 terrorist attacks, President George W. Bush suspended refugee processing. It was later restarted.

In the last budget year, the U.S. has accepted 84,995 refugees of which 12,587 were from Syria. Former President Barack Obama set the refugee limit for the current budget year at 110,000.

Sources close to Trump tell Fox News he has plans to cut that by more than half to 50,000.

In an interview with CBN, Trump said persecuted Christians from Syria would get priority.

“They’ve been horribly treated. Do you know if you were a Christian in Syria it was impossible, at least very tough to get into the United States? If you were a Muslim you could come in, but if you were a Christian, it was almost impossible and the reason that was so unfair, everybody was persecuted in all fairness, but they were chopping off the heads of everybody but more so the Christians. And I thought it was very, very unfair. So we are going to help them.”