Rosie O'Donnell pictured at SiriusXM's "It's Not Over" Town Hall in Las Vegas, April 2, 2015. Getty Images

Rosie O'Donnell has reignited her feud with Donald Trump by calling him "mentally unstable" in a new tweet posted Sunday. The former co-host of ABC's talk show "The View" also called on to the people of United States, reminding them only three weeks were left to stop Trump from taking the White House.

"Donald Trump is mentally unstable," O'Donnell wrote, while sharing a link to a CNN article, adding there are "less than 3 weeks to stop him America."

The article, which was shared by O'Donnell, was about biographer Harry Hurt III, who has been critical of Trump. Hurt, who penned "Lost Tycoon: The Many Lives of Donald J. Trump," told CNN that he was asked to leave the Trump International Golf Club in West Palm Beach after introducing himself to the president-elect Friday.

Hurt said Trump's behavior was "inappropriate" after he claimed in a Facebook post that he received a "tongue lashing from the President-elect."

"Trump said, 'You were rough on me, Harry. Really rough. That shit you wrote,'" read the Facebook post. "Among the juicy tidbits in Hurt’s tome was Ivana Trump’s allegation in a sworn deposition that Trump had 'raped' her during their divorce battle."

After reading the article on CNN, O'Donnell took a jab at the business mogul.

In November, O'Donnell came under fire for raising the possibility of Trump's youngest son Barron being autistic. She later explained her comments, saying she questioned if Barron was autistic because her daughter was recently diagnosed with the condition and she recognizes the symptoms.

“Here is how it went down,” O’Donnell wrote in a statement. “My 3.5 year old daughter Dakota was diagnosed in September with HFA — high functioning autism. I have been immersed in that world/reality since learning — reading — asking questions. It’s all autism — all the time for the newly diagnosed. As we try to grab onto anything to keep us standing, the knowledge we r not alone there r others living this too.”

She went on to write: “But this autism subject — had nothing to do with Donald, though i admit he does trigger me in all ways — i have no ill will for his children — or any children — and if u knew anything about me — u would know that.”

Later, TMZ reported that Trump's wife Melania hired Charles Harder, who sent a letter threatening to sue over a video captioned, “Barron Trump Autistic? #StopTheBullying,” which was tweeted out by O’Donnell.