Hillary Clinton's campaign responded late Monday evening to Donald Trump's suggestion that there should be "extreme vetting" for immigrants to the United States, and said his idea is untenable.

"This so-called 'policy' cannot be taken seriously," campaign spokesman Jake Sullivan said in a statement.

"How can Trump put this forward with a straight face when he opposes marriage equality and selected as his running mate the man who signed an anti-LGBT law in Indiana?" the statement added. "It's a cynical ploy to escape scrutiny of his outrageous proposal to ban an entire religion from our country and no one should fall for it."

Trump promised Monday during a campaign rally in Youngstown, Ohio, that he'd impose a strict vetting process on all immigrants coming into the United States. The idea, he explained, is that the U.S. government would weed out those who subscribe to extreme ideologies.

"In the Cold War, we had an ideological screening test," he said. "The time is overdue to develop a new screening test for the threats we face today — I call it 'extreme vetting.' I call it 'extreme, extreme vetting.'"

"Our country has enough problems. We don't need more. And these are problems like we've never had before," he added.

He continued, elaborating on his plan to weed out dangerous immigrants.

"In addition to screening out all members or sympathizers of terrorist groups, we must also screen out any who have hostile attitudes towards our country or its principles – or who believe that Sharia law should supplant American law," he said. "Those who do not believe in our Constitution, or who support bigotry and hatred, will not be admitted for immigration into the country.

"Only those who we expect to flourish in our country – and to embrace a tolerant American society – should be issued visas," he added. "To put these new procedures in place, we will have to temporarily suspend immigration from some of the most dangerous and volatile regions of the world that have a history of exporting terrorism."