Former Gov. Mitt Romney on Friday slammed President Trump for how he has handled Charlottesville and warned that there may be "an unraveling of our national fabric" if he doesn't apologize.

In a lengthy post on Facebook, the 2012 GOP presidential nominee wrote that the "potential consequences are severe in the extreme" and he must take extreme action in response.

"He should address the American people, acknowledge that he was wrong, apologize. State forcefully and unequivocally that racists are 100% to blame for the murder and violence in Charlottesville," wrote Romney, who served as governor of Massachusetts from 2003 until 2007.

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He continued that the president should, "Testify that there is no conceivable comparison or moral equivalency between the Nazis--who brutally murdered millions of Jews and who hundreds of thousands of Americans gave their lives to defeat--and the counter-protesters who were outraged to see fools parading the Nazi flag, Nazi armband and Nazi salute."

Romney said that the president must disavow former KKK grand wizard David Duke, who has celebrated Mr. Trump's comments this week.

"And once and for all, he must definitively repudiate the support of David Duke and his ilk and call for every American to banish racists and haters from any and every association," Romney wrote.

Romney said that what Mr. Trump communicated on Tuesday "caused racists to rejoice, minorities to weep and the vast heart of America to mourn."

"This is a defining moment for President Trump. But much more than that, it is a moment that will define America in the hearts of our children," Romney said. "They are watching, our soldiers are watching, the world is watching. Mr. President, act now for the good of the country."

During the 2016 presidential campaign, Romney blasted Mr. Trump and said that he was unfit to serve as president.

"Let me put it plainly, if we Republicans choose Donald Trump as our nominee, the prospects for a safe and prosperous future are greatly diminished," he said in a speech at the University of Utah. "His is not the temperament of a stable, thoughtful leader. His imagination must not be married to real power."