The "Homecoming Queen" at a traditionally black US university has sent a letter to President Barack Obama, complaining that her win had been questioned on campus because she is white.

But after her letter riled students at Hampton University in Virginia, beauty pageant winner Nikole Churchill issued a public apology, saying she had taken "the comments of a few and blew them out of all proportion."

Churchill, a tall, raven-haired woman who, like Obama, grew up in Hawaii, wrote to the president after winning her university's beauty pageant last week.

"It would be much easier to say that possibly some were not accepting of the news because I wasn?t the most qualified contestant; however, the true reason for the disapproval was because of the color of my skin. I am not African American," the nursing student wrote to the president.

She asked the president for help, suggesting that he visit Hampton University to convince students to "stop focusing so much on the color of my skin and doubting my abilities to represent, but rather be proud of the changes our nation is making towards accepting diversity.

"I am hoping that you can assist me in opening some closed minds," Churchill said.

That brought a raft of reactions, including from students at Hampton University who said race had nothing to do with their disgruntlement at Churchill's election.

"Black or white, this young lady is not qualified to be the face of Hampton University as she is not in tune with the wants, needs, and desires of the student body at large," a person who signed themselves as a graduate of the university commented on the website of Essence, a magazine for black women.

"Although some are outraged by her race, I think most are upset because this young lady has no ties to the student body. She is a transfer student who attends an HU satellite campus. She has never lived in a dorm, eaten in the cafe, or spent time in the Student Center."

Churchill has issued a statement on the university's website, regretting having written to Obama and apologizing for drawing negative attention to Hampton University, which she hailed as being a long-time pioneer of diversity.

The next instalment in the saga is likely to come on October 21, when Churchill is due to be formally "crowned" during Hampton University's week-long homecoming celebrations.