Outgoing White House adviser Omarosa Manigault Newman said it was difficult to contend with the lack of diversity in President Trump's staff.

“It has been very, very challenging being the only African-American woman in the senior staff,” she told ABC’s “Nightline” on Thursday. “There was a lack of diversity that I will acknowledge.”

Manigault Newman, who is black, also said it “was very lonely” working with fellow senior staff members who “had never worked with minorities, didn't know how to interact with them.”

Manigault Newman maintained that she will be leaving Jan. 20 after resigning earlier this week. Reports conflicting with her own account said she was fired by chief of staff John Kelly and had to be removed from the White House.

An official White House statement on Wednesday said she "resigned yesterday to pursue other opportunities."

Earlier Thursday, Manigault Newman said there "were a lot of things that I observed during the last year that I was very unhappy with."

"But when I have my story to tell as the only African-American woman in this White House, as a senior staff and assistant to the president, I have seen things that have made me uncomfortable, that have upset me, that have affected me deeply and emotionally, that has affected my community and my people and when I can tell my story, it is a profound story that I know the world will want to hear," Manigault Newman added.

A friend of the former adviser, businessman Armstrong Williams, told the Washington Post that Manigault Newman disagreed with Trump's endorsement of Republican Alabama Senate candidate Roy Moore, who lost Tuesday to Democrat Doug Jones. Moore faced numerous sexual misconduct allegations and had made several racially insensitive statements.

Manigault Newman served in the Office of Public Liaisons and has known Trump since being a contestant on first season of the "The Apprentice."