Republican presidential candidate Donald Trump on Tuesday defended his proposal to ban Muslims from entering the United States, comparing his plan to the World War Two detainment of Japanese-Americans and others in dismissing growing outrage from around the world.
In an unprecedented intervention in a US presidential race, a spokeswoman for British Prime Minister David Cameron called Trump's comments "divisive, unhelpful and quite simply wrong".
The White House called on Republicans to say they would not support Trump, currently the party's front-runner for the November 2016 election. US Homeland Security Secretary Jeh Johnson said his comments could undermine US security.
The prime ministers of France and the United Kingdom, Canada's foreign minister, the United Nations and Muslims in Asian countries all denounced the real-estate mogul's comments.
But Trump said his ideas were no worse than those of then-President Franklin D Roosevelt, who oversaw the internment of more than 110,000 people in US government camps after Japanese forces bombed Pearl Harbor on December 7, 1941.
"What I'm doing is no different than FDR," Trump said on ABC's "Good Morning America" program.
"We have no choice but to do this," he said. "We have people that want to blow up our buildings, our cities. We have to figure out what's going on."
Trump said on ABC's "World News Tonight" the ban would be "short term". He said the ban could be lifted "very quickly if our country could get its act together".
Trump also pressed his case in fractious appearances on MSNBC and CNN.
On Monday, he called for blocking Muslims, including would-be immigrants, students, tourists and other visitors, from entering the country following last week's California shooting spree by two Muslims who authorities said were radicalised.
It was the most dramatic response by a presidential candidate following the San Bernardino, California, rampage, even as other Republicans have called for a suspension of President Barack Obama's plan to allow in 10,000 refugees from Syria.
Homeland Security Secretary Johnson said Trump's proposal could thwart US efforts to connect with the Muslim community, and the Pentagon issued a similar warning. Secretary of State John Kerry said Trump's ideas were not constructive.
A Trump campaign spokeswoman, asked for comment on US officials' reactions, did not address their criticism.
White House spokesman Josh Earnest said Trump's comments disqualify him from being president and said other Republican candidates should disavow him "right now."
Trump's stance could help Democrats
Trump leads the Republican pack seeking the White House in 2016 with 35 percent of support in a recent Reuters/Ipsos poll. Nearly all of Trump's rivals criticised his proposal on Monday.
Republican National Committee Chairman Reince Priebus told the Washington Examiner political news website that the United States must combat terrorism "but not at the expense of our American values".
The two top officials in the Republican-controlled Congress – House of Representatives Speaker Paul Ryan and Senate Majority Leader Mitch McConnell – criticised Trump but said they would support their party's eventual nominee.
But other Republicans warned that if Trump is the party's choice for the November 2016 election, his stance could hurt in a matchup with Democratic front-runner Hillary Clinton.
"All this helps is his buddy Hillary Clinton, for sure," presidential hopeful and former Florida Governor Jeb Bush told reporters in Manchester, New Hampshire. "I don't think Republicans are going to abide this language that guarantees that Hillary Clinton has a far better chance of winning."
Democrats, meanwhile, blamed Republicans for Trump's extreme language and warned it could help him with primary voters.
"Unfortunately, Trump is leaning into the kind of fear of progress that very well could help him win the nomination," Huma Abedin, a top aide to Clinton, said in a fundraising email declaring her own Muslim faith.
Clinton said at a campaign event in New Hampshire that Trump's Muslim ban was a "shameless and dangerous idea" which played right into the hands of extremists.
Polls have shown a stark divide between Republicans and Democrats in how they view Muslims, who number about 3 million in the United States, or less than 1 percent of the population.
Some conservative commentators, such as pundit Ann Coulter, came to Trump's defence. Columnist Adriana Cohen wrote in the Boston Herald that Trump should go a step further and call for closing the US border entirely.
Trump on Tuesday tweeted a link to a poll showing that 68 per cent of his supporters would vote for him if he left the Republican Party and ran as an independent.
Still, Thomson Reuters data showed sentiment on social media toward the outspoken billionaire became substantially more negative compared with that before his proposal on Monday afternoon to ban Muslims.
Trump's campaign dismissed criticism that his plan would likely be unconstitutional for singling out people based on their religion. Spokeswoman Katrina Pierson told MSNBC that the US Constitution, which guarantees freedom of religion, does not apply to people outside the United States.
The reaction from abroad was largely one of outrage. French Prime Minister Manuel Valls said on Twitter, "Mr Trump, like others, is feeding hatred and misinformation."
A group started a petition to revoke Trump's honorary degree from Robert Gordon University in Scotland.
"We have never been as far removed from what we've just heard in the United States," Canadian Foreign Minister Stephane Dion said. The United States' northern neighbour does not usually comment on elections in other countries.
A spokesman for United Nations Secretary-General Ban Ki-moon rejected Trump's comments, and Muslims in Pakistan and Indonesia denounced him.
Two international refugee organisations rejected Trump's comments, saying US presidential campaign rhetoric threatens resettlement efforts.
Trump warned repeatedly that an attack on the scale of September 11, 2001, could happen again if officials do not act first. He said that he did not know how long a ban would remain in place and that Muslim Americans would be allowed into the country after overseas trips.
Trump told MSNBC that people would be asked about their religion at US borders and that the ban would extend to Muslim leaders of other nations. He said he would not support internment camps.
Some observers poked fun at Trump.
The Democratic mayor of St. Petersburg, Florida, Rick Kriseman, said in a tongue-in-cheek tweet that he was barring Trump from visiting the city.
"I am hereby barring Donald Trump from entering St Petersburg until we fully understand the dangerous threat posed by all Trumps," Kriseman wrote.