Cable sports network ESPN has denounced comments made by anchor Jemele Hill after she called President Donald Trump "a white supremacist" and a "bigot".
The African-American anchor tweeted on Monday that he was the "most ignorant, offensive president of my lifetime".
In a statement, the network said her "inappropriate" remarks did not represent the company and that it had addressed the issue with her.
White House spokeswoman Sarah Sanders called the tweets "outrageous".
She said during a news conference on Wednesday she was not certain whether President Trump was aware of the comments, but that it was "one of the more outrageous comments that anyone could make, and certainly something that I think is a fire-able offense by ESPN".
Donald Trump is a white supremacist who has largely surrounded himself w/ other white supremacists.— Jemele Hill (@jemelehill) September 11, 2017
Ms Hill, a co-host of the SportsCenter programme, called the president a bigot and criticised his supporters.
"His rise is a direct result of white supremacy. Period", she tweeted.
"The height of white privilege is being able to ignore his white supremacy, because it's of no threat to you. Well, it's a threat to me."
He is unqualified and unfit to be president. He is not a leader. And if he were not white, he never would have been elected— Jemele Hill (@jemelehill) September 12, 2017
Critics of Mr Trump have accused him of racism after his response to deadly clashes at a far-right rally, held by neo-Nazis and white supremacists, in Charlottesville, Virginia, last month.
One person was killed when a car rammed a crowd of people who were against the rally.
Mr Trump initially failed to denounce the groups responsible for the rally, and later suggested both hate groups and counter protesters were to blame for the violence.
Ms Hill's tweets drew ire online, where Twitter users called for her to be fired.
But NFL quarterback Colin Kaepernick, who made national headlines last year for kneeling during the national anthem before games to protest police brutality, expressed his support for Ms Hill in a tweet.
ESPN said Ms Hill "recognises her actions were inappropriate", but declined to say whether she would be punished.