Comedian Rosie O'Donnell took to the Twittersphere on Sunday to offer sharp criticism of President-elect Donald Trump, saying that Trump is "mentally unstable" and must be stopped before taking office three weeks from now.

"DONALD TRUMP IS MENTALLY UNSTABLE," O'Donnell tweeted afternoon, linking to a CNN.com story about a biographer who alleged that Trump ejected him from his golf course over the weekend.

"LESS THAN 3 WEEKS TO STOP HIM AMERICA," she added.

She later took to Twitter again late Sunday to say that she doesn't think Trump is mentally OK.

"DT IS MENTALLY ILL," O'Donnell tweeted, linking to a BuzzFeed story about a college student who painted several Trump quotes on her body, adding the hashtags "#Resist" and "#Focus."

Trump and O'Donnell have had a somewhat tumultuous past that was resurrected during a Republican primary debate in Aug. 2015 and again during a debate with Hillary Clinton in September.