Thousands of Americans have pledged online to stand in solidarity with Muslims in the United States amid suggestions from President-elect Donald Trump’s camp that he is mulling a national registry for immigrants from Muslim countries.

On Friday, more than 13,000 people had signed a pledge on website Register US, promising to register as Muslims in the event of a national Muslim database being rolled out, so as “to stand together with Muslims across the country.”

The online movement reflects a divided nation in the aftermath of Trump’s presidential election win, that followed a campaign marked by hardline rhetoric on immigration.

In a Reuters interview this week, Kansas Secretary of State Kris Kobach, who media reports say is a key member of Trump’s transition team, said a group advising Trump on immigration could recommend the reinstatement of a national registry of some Muslim immigrants and visitors who enter the United States on visas from countries where extremist organizations are active.

However, Jason Miller, communications director of Trump’s transition team, said in an emailed statement to the Thomson Reuters Foundation on Friday that “President-elect Trump has never advocated for any registry or system that tracks individuals based on their religion, and to imply otherwise is completely false.”

Last year, as he was campaigning to become the Republican Party’s presidential nominee, Trump drew widespread condemnation when he agreed on-camera to the idea of a government database to keep track of Muslims in the United States.

Many among those who took the pledge on Register US’s website posted on Twitter a message, prepared by the group, detailing their intentions.

“If Trump requires Muslims to register with the government, I pledge to register as Muslim too,” the message said.

Twitter user Sam Martin, from Florida, was among thousands who voiced his support for the initiative.

“If anyone'(s) name is entered into a database driven by GOP/Trump bigotry, this is how I say, ‘It’s wrong to do this!’,” he wrote in a comment on Twitter.

Registering Muslims in the United States has been likened to the U.S. government’s internment of Japanese-Americans in camps during World War Two – for which an official apology was later issued – and with Nazi Germany’s laws that required Jews to register with authorities.

In a statement posted on Twitter earlier this week, the head of the Anti-Defamation League (ADL), Jonathan Greenblatt, was quoted as saying that “If one day Muslims will be forced to register, that is the day that this proud Jew will register as a Muslim.”

Register US co-founder, Rebecca Green, who works in brand marketing in New York City, said she was encouraged by the public’s response since launching the website with two friends earlier this week.

“We see this effort as a plea to American values to not become the kind of country that keeps lists based on religion,” she told the Thomson Reuters Foundation in an email.

“Nothing is more anti-American than a registry based on religion.”

There were about 3.3 million Muslim people living in the United States in 2015, according a recent estimate by the Washington-D.C.-based Pew Research Center, a non-partisan think tank.