U.S. Senate candidate Loretta Sanchez has apologized after a videotape surfaced showing her making a whooping cry in reference to Native Americans during an apparent joke.

Speaking to delegates at a state Democratic convention in Southern California Sunday, the 10-term congresswoman said she said something offensive "and for that I sincerely apologize."

The video, which was shared on social media, shows Sanchez tapping her hand over her open mouth and making a whooping sound while speaking to a group of delegates Saturday.

Her chief rival in the Senate race, Attorney General Kamala Harris, called the gesture shocking.

Sanchez said everyone makes mistakes and defended her record on civil rights, human rights and Native American rights.

Sanchez said American Indians have "a great presence in our country and many of them are supporting our election."

Harris, whose mother was an immigrant from India, said, "There is no place for that in our public discourse."

The incident came during a convention in which the 2016 Senate race played out among speeches and partying. The two Democrats are the leading candidates for the seat being vacated by retiring Sen. Barbara Boxer.

On Saturday, Harris defended her qualifications on foreign affairs and national defense after Sanchez had suggested she doesn't have the skills for the job in Washington.

Harris told reporters that voters next year will determine who is qualified for the Senate seat, and her experience as a two-term attorney general and a former local prosecutor gave her the background she would need on Capitol Hill.

"I feel certainly equipped to have a sense of what California needs and wants as it relates to many issues," Harris said. As a career prosecutor, "I know the stuff they do in Washington actually impacts California."

Sanchez, who entered the race Thursday, spent Saturday dashing to and from convention meetings, shaking dozens of hands and posing for snapshots. When she entered the race last week, she said that her long experience in defense and foreign affairs on Capitol Hill was essential in "perilous times," drawing a contrast with Harris.