Mitt Romney called on President Donald Trump Friday to apologize for his comments about Charlottesville, Virginia, saying the President’s remarks this week “caused racists to rejoice.”

“The potential consequences are severe in the extreme,” Romney wrote in a Facebook post. “Accordingly, the president must take remedial action in the extreme. He should address the American people, acknowledge that he was wrong, apologize.”

He said that Trump’s remarks — in which he blamed “both sides” for inciting violence, an equivocation between neo-Nazis and those protesting them — had a hurtful impact on the nation.

“Whether he intended to or not, what he communicated caused racists to rejoice, minorities to weep, and the vast heart of America to mourn,” Romney wrote. “His apologists strain to explain that he didn’t mean what we heard. But what we heard is now the reality, and unless it is addressed by the president as such, with unprecedented candor and strength, there may commence an unraveling of our national fabric.

Romney also called this a “defining moment” for Trump.

“But much more than that, it is a moment that will define America in the hearts of our children,” he concluded. “They are watching, our soldiers are watching, the world is watching. Mr. President, act now for the good of the country.”

Romney was a forceful critic of Trump during his 2016 campaign, at one point even calling him “a phony, a fraud.” Trump fired back that Romney was a “choke artist” and “failed candidate” in the 2012 election.

However, after Trump won the election, the two mended their relationship and Trump even considered appointing Romney as his secretary of state.

This isn’t the first time Romney spoke out about Charlottesville. He tweeted earlier this week, “No, not the same. One side is racist, bigoted, Nazi. The other opposes racism and bigotry. Morally different universes.”