"Friday nights are always my worst night of sleep because I'm up reflecting on the things I should or shouldn’t have said on my live show," Maher said in a statement.
"Last night was a particularly long night as a I regret the word I used in the banter of a live moment. The word was offensive and I regret saying it and am very sorry."
During an interview with Nebraska senator Ben Sasse, the Republican politician invited Maher to visit the state and said, "We'd love to have you work in the fields with us."
Maher responded, "Work in the fields? Senator, I'm a house nigger."
The comment drew a mixed reaction from the Real Time audience – "It's a joke," Maher said – and widespread criticism on social media, with everyone from Black Lives Matter activist Deray McKesson to Chance the Rapper demanding that HBO fire the host.
In a statement Saturday, HBO said, "Bill Maher's comment last night was completely inexcusable and tasteless. We are removing his deeply offensive comment from any subsequent airings of the show." It's unclear whether the network will seek further punishment against Maher.
Sasse, who also received criticism for not chiding Maher following the racial slur, said in a series of tweets Saturday, "Here's what I wish I’d been quick enough to say in the moment: 'Hold up, why would you think it's OK to use that word?' The history of the n-word is an attack on universal human dignity. It's therefore an attack on the American Creed. Don't use it."