Congresswoman Rashida Tlaib says she regrets booing 2016 Democratic nominee Hillary Clinton at an event in Iowa.
It follows some criticism after footage of Friday’s event was posted on Twitter by an audience member.
Ms Tlaib, also a Democrat, led the booing in response to Ms Clinton saying in a documentary that “nobody likes” presidential hopeful Bernie Sanders.
Ms Tlaib later said that she had allowed her feelings about Ms Clinton’s remarks “to get the best of me”.
“I know what is at stake if we don’t unify over one candidate to beat [President Donald] Trump and I intend to do everything possible to ensure that Trump does not win in 2020,” she tweeted.
“In this instance, I allowed my disappointment with Secretary Clinton’s latest comments about Senator Sanders and his supporters get the best of me. You all, my sisters-in-service on stage, and our movement deserve better.”
How did the booing come about?
The Michigan representative was taking part in a panel event with fellow Democratic congresswomen Pramila Jayapal and Ilhan Omar, held at a folk music concert in Iowa on Friday.
When the moderator Dionna Langford brought up the escalating feud between Ms Clinton and Senator Sanders, members of the audience began to boo.
Ms Langford interrupted and said: “We’re not going to boo, we’re classy here.”
At this point Ms Tlaib interjected: “No no, I’ll boo.”
As Ms Jayapal and Ms Omar laughed, Ms Tlaib added: “You all know I can’t be quiet. No, we’re going to boo. That’s alright, the haters will shut up on Monday when we win.”
Monday’s caucuses will be the first formal test this year of Democratic voters’ preferences. Senator Sanders is the frontrunner, with a slight lead ahead of his nearest rival, former Vice President Joe Biden.
Ms Tlaib’s booing attracted a mixed reaction online.
Neera Tanden, president of the Center for American Progress, said that it reminded her of President Trump’s supporters chanting “Lock Her Up” in 2016.
Others said the booing was justified, with left-wing writer Annie Shields responding that Ms Clinton “should stop publicly criticising one of the Dem front runners in the interest of party unity”. Filmmaker Michael Moore said he was “so proud” of Ms Tlaib.