Republican presidential hopeful Donald Trump has provoked condemnation from across the political spectrum, by saying Muslims should be banned from entering the US.
Republicans, Democrats, Muslim leaders, the UN and foreign leaders criticised the call as dangerous and divisive.
Mr Trump said many Muslims nursed a "hatred" towards America.
He said they should be banned "until our country's representatives can figure out what is going on".
His campaign manager said that would apply to "everybody" - would-be immigrants and tourists. But Mr Trump told Fox News it would "not apply to people living in the country", adding that Muslims serving in the US military would "come home".
Mr Trump's statement was delivered as the US comes to terms with its deadliest terror attack since 9/11.
Last week a Muslim couple, believed to have been radicalised, opened fire and killed 14 people at a health centre in San Bernardino.
Mr Trump's proposed ban prompted a horrified reaction from Republicans and others.
White House Press Secretary Josh Earnest later challenged the Republican party to denounce the leading candidate, and said that the proposal "disqualifies him from serving as president".
Mr Earnest said that the Trump campaign had a "dustbin of history" quality to it, calling the candidate a "carnival barker" with "fake hair".
The UK's Conservative Prime Minister David Cameron said they were "divisive, unhelpful and quite simply wrong", while his French counterpart Manuel Valls said Mr Trump "stoked hatred".
UN refugee agency UNHCR said it was concerned that the rhetoric was putting an "incredibly important" resettlement programme for vulnerable Syrian refugees at risk.
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"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.
"These are not just words... Trump and Carson's mainstreaming of Islamophobia in the election is inciting discrimination, hate crimes, violent attacks against Muslims and mosques."
Mr Trump took part in heated interviews on several US television networks on Tuesday, defending the proposal and saying it was a temporary measure to prevent "many more World Trade Centers".
On ABC's Good Morning America, he said "what I'm doing is no different than FDR," referring to policies implemented by President Franklin Roosevelt during World War Two against Japanese, German and Italian people in the US. Some of those measures saw over 100,000 people detained in government camps.
At one point during a lengthy interview on MSNBC, presenter Joe Scarborough forced the network into a commercial break after the candidate repeatedly talked over journalists, refusing to answer questions.
Mr Trump's statement to reporters on Monday said polling by the Center for Security Policy, a conservative think-tank, suggested that 25% of Muslims in the US believed violence against America was justified.
"The hatred is beyond comprehension. Where this hatred comes from and why, we will have to determine.
"Until we [do]... our country cannot be the victims of horrendous attacks by people that believe only in jihad."
It is not the first time the New York billionaire has come under fire for anti-Muslim remarks.
After the terror attacks in Paris, he suggested they register on a database and he said the US should refuse all Syrian refugees. Then he said thousands of Muslims in New Jersey cheered during 9/11, despite no evidence.
His travel ban pledge sparked loud cheers when he outlined it at a South Carolina rally hours after his initial statement.
A handful of supporters backed Mr Trump online, with controversial conservative commentator Ann Coulter tweeting: "GO TRUMP, GO!"
And another of the Republican frontrunners, Ted Cruz, praised Mr Trump "for standing up and focusing America's attention on the need to secure our borders", although he said he disagreed with the policy.
Out on a limb - how other 2016 hopefuls reacted
- "ridiculous position" - New Jersey Governor Chris Christie
- "dangerous overreaction" - businesswoman Carly Fiorina
- "offensive and outlandish" - Florida Senator Marco Rubio
- "unhinged" - ex-Florida Governor Jeb Bush
- "outrageous divisiveness" - Ohio Governor John Kasich
- "downright dangerous" - S Carolina Senator Lindsey Graham
- "not my policy" - Texas Senator Ted Cruz
- "fascist demagogue" - ex-Maryland Governor Martin O'Malley
- "reprehensible, prejudiced and divisive" - Hillary Clinton
- "demagogue" - Vermont Senator Bernie Sanders