The White House sent a warning to Donald Trump Thursday: Attacking Michelle Obama is off limits.

The first lady blasted Trump without actually naming him during a campaign speech for Democrat Hillary Clinton on Thursday. The White House followed up with its own message for the Republican presidential candidate.

"I can't think of a bolder way for Donald Trump to lose even more standing than he already has than by engaging the first lady of the United States," principal deputy White House press secretary Eric Schultz said on Air Force One, Politico reported.

During a Clinton rally in Manchester, N.H., Obama addressed the recently released audio of comments Trump made in 2005 that were sexually sexually aggressive and graphic.

"I can't believe I'm saying a candidate for president of the United States has bragged about sexually assaulting women," Obama said, per CNN.

"I can't stop thinking about this. It has shaken me to my core in a way I could not have predicted. I know this is a campaign, but this isn't about politics. It's about basic human decency."

Trump brushed off the comments he made as "locker room talk." Since the tape was made public last Friday, several women have come forward and claimed Trump sexually assaulted them. 

Obama went onto say the comments were forcing women to recollect painful memories of when they were harassed in their offices or sexually assaulted.

"The truth is it hurts. It hurts," she said.

"It's like that sick, sinking feeling you get when you are walking down the street, minding your own business and some guy yells out vulgar words about your body or when you see that guy at work that stands a little too close, stares a little too long and makes you feel uncomfortable in your own skin," she said, as the crowd went silent.

While she didn't mention her husband, President Barack Obama, she said Trump's comments did not reflect how the men in her family discuss women.

"I can tell you the men in my life do not talk about women like this. I know my family is not unusual," she said adding, "they are loving fathers who are sickened by the thought of their daughters being exposed to this kind of vicious language about women."

Mrs. Obama's comments are some of the most forceful of a week in which scores of Republican leaders abandoned Trump after a 2005 video became public in which the GOP nominee is heard bragging about how his fame allowed him to "do anything" to women. Sen. Kelly Ayotte, R-N.H., who is in a tight re-election campaign, said over the weekend that she no longer plans to vote for him.

Trump has played down the comments, insisting they were "locker room talk" and that he never did anything of the things he bragged about on the tape. Since then, the New York Times and the Palm Beach Post reported stories about three women who alleged Trump had inappropriately touched them. Separately, a People Magazine reporter wrote a detailed first-person account of being attacked by Trump while interviewing the businessman and his wife, Melania Trump.

Trump denies the allegations.