"I have a standing invitation to this president," he said at the Muslim Caucus Conference in Washington. "Go to section 60, face the tombstones, and you will see all races, all faiths defending this country. That is true America."
Khan is the father of a U.S. Army captain who was killed in Iraq.
In one of the Democratic National Convention's most popular speeches from a non-elected official, Khan told Donald Trump "you have sacrificed nothing."
Trump, at the time, responded in an interview with ABC News' George Stephanopoulos by saying, "I think I've made a lot of sacrifices. I work very, very hard."
Trump also said, "If you look at his wife, she was standing there. She had nothing to say. She probably -- maybe she wasn't allowed to have anything to say. You tell me."
Khan shared the stage on Tuesday with Omar and condemned the chants aimed at her, along with three other women of color.
"Those who chanted at the North Carolina rally -- an illegal and unconstitutional rally -- they have forsaken the maxims of enlightenment and equality and inclusiveness," Khan said.
Omar responded on Tuesday, "people will say you know his remarks are racist, and we'll forget the inherent racism that has always been part of him."