The 59-year-old actor-host said she does not want to provide a platform to the POTUS as that will mean giving undue importance to him, reported FoxNews.com.
"There's nothing I'm going to say to him that's gonna change him and I don't want to give him a platform because it just... validates him.
"And I can't have someone that I feel is not only dangerous for the country and for me personally as a gay woman, but to the world. I don't want him on the show," Ellen said on her show.
Kelly, 46, who has a bitter history with Trump, revealed that it was the current American president who pushed her to resign from Fox News after 12 years.
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"Donald Trump has a way of clarifying one's life choices and that was true in my case, too. Just as I was wondering where I wanted to be and what I wanted to do, the universe came and showed... me what I wanted to do," she said on "The Ellen DeGeneres Show".
Trump had lashed out repeatedly at Kelly after she moderated a Republican presidential debate in August 2015 and the feud continued for a long time.