Republican presidential candidate Donald Trump has been criticised by White House rivals for saying he would implement a database to keep track of Muslims in the United States and require them to register in response to the attacks in Paris.
Trump, speaking to an NBC News reporter after a campaign appearance in Iowa on Thursday night, was asked if there should be a database to monitor Muslims in the United States.
"I would certainly implement that, absolutely," he said in on-camera comments.
Asked how that differed from efforts last century to track Jews in Nazi Germany, he said: "You tell me."
On Friday, Trump deflected criticism of the remarks, saying in a tweet: "I didn't suggest a database - a reporter did. We must defeat Islamic terrorism & have surveillance, including a watch list, to protect America."
His comments came amid renewed security concerns following the Islamic State attacks in Paris last week that killed at least 130 people, and a political fight over US plans to take in 10,000 refugees from Syria.
Two Republican presidential rivals, former Florida Governor Jeb Bush and Ohio Governor John Kasich, were the most critical of the database proposal. Bush called it "just wrong".
"It's manipulating people's angst and their fears," he said on CNBC.
"That's not strength. That's weakness."
Kasich, whose Super PAC is launching a $US2.5 million ($A3.47 million) series of attacks against Trump, said the proposal proved the real estate mogul was not worthy of the White House.
"The idea that someone would have to register with the federal government because of their religion strikes against all that we have believed in our nation's history," Kasich said in a statement.
"Donald Trump is unable to unite and lead our country."