Donald Trump has rejected criticism that his proposal to ban Muslims from entering the US is un-American as critics compared him to Adolf Hitler.
The Republican presidential candidate said what he is proposing is "no different" to the actions of president Franklin Roosevelt, "who was highly respected by all" despite his wartime measures that included putting Japanese-Americans in internment camps in the US.
Mr Trump told ABC's Good Morning America that banning Muslims is warranted because the US is essentially at war with Muslim extremists who have launched attacks including last week's shooting in San Bernardino, California, that killed 14.
"We are now at war," he said, adding: "We have a president who doesn't want to say that."
Mr Trump's proposal has been denounced by many of his fellow Republican presidential candidates.
Mr Trump has called for a "total and complete shutdown of Muslims entering the United States".
The proposed ban would apply to immigrants and visitors alike, a sweeping prohibition affecting all adherents of a religion practised by more than a billion people worldwide. He said in a statement that such a ban should stand "until our country's representatives can figure out what is going on".
"Until we are able to determine and understand this problem and the dangerous threat it poses, our country cannot be the victims of horrendous attacks by people that believe only in jihad, and have no sense of reason or respect for human life."
His Republican rivals were quick to reject the latest provocation from a candidate who has delivered no shortage of them. "Donald Trump is unhinged," former Florida governor Jeb Bush said on Twitter. "His 'policy' proposals are not serious."
John Kasich slammed Mr Trump's "outrageous divisiveness", while a more measured Ted Cruz, who has always been cautious about upsetting the tycoon's supporters, said: "Well, that is not my policy."
Mr Trump's plan also drew criticism from the heads of the Republican Party in Iowa, New Hampshire and South Carolina, the first three states to vote in next year's presidential primaries.
"It is un-Republican. It is unconstitutional. And it is un-American," said Jennifer Horn, chairwoman of the Republican Party of New Hampshire.
"Donald Trump sounds more like a leader of a lynch mob than a great nation like ours," said Nihad Awad, national executive director of the Council on American-Islamic Relations. "He and others are playing into the hands of Isis (Islamic State). This is exactly what Isis wants from Americans: to turn against each other."
Mr Trump's proposal came a day after Barack Obama spoke to the nation from the Oval Office about the shootings in San Bernardino, which the president described as "an act of terrorism designed to kill innocent people".
The leader of the US House of Representatives, Republican Paul Ryan, dismissed Mr Trump's comments, saying such views are "not what this party stands for and more importantly it's not what this country stands for".
Speaking to reporters after a closed-door Republican caucus meeting, Mr Ryan said: "Freedom of religion is a fundamental constitutional principle. This is not conservatism, what was proposed yesterday is not what this party stands for and more importantly it's not what this country stands for."
The Wisconsin Republican said many Muslims serve the country and work in Congress, and the "vast, vast majority of them are peaceful".