"I was so sad that people thought it was racist," Barr told Fox News host Sean Hannity. She said the tweet referencing former Obama adviser Valerie Jarrett - "muslim brotherhood & planet of the apes had a baby = vj" - was a bid to seek accountability for the 2015 international agreement limiting Iran's nuclear program.
She did not clarify what she believed was Jarrett's involvement in the agreement.
"I made a mistake obviously. It cost me everything, my life's work. And I paid the price for it. But no, I did not know she (Jarrett) was black," she said.
Jarrett was born in Iran to parents of European and African-American descent. She said on Wednesday she did not intend to watch Barr's interview.
Addressing Jarrett directly, Barr said on Thursday: "I'm sorry you feel harmed and hurt because I never meant that."
Barr's tweet caused a storm of outrage and the ABC network swiftly canceled the revival of her top-rated comedy series "Roseanne" about a working-class American family in the era of President Donald Trump.
ABC has since announced the show will return in October as a spinoff called "The Conners" with all the main characters except Barr, who will have no financial or creative involvement.
"I have apologized a lot. I feel that I have apologized and explained and asked for forgiveness and made recompense," Barr said on Thursday, adding that she has made donations to "several African-American things."