Former New York congressman Anthony Weiner will plead guilty to sending obscene material to a minor, US media report.
The charge stems from sexually charged text messages he allegedly exchanged with a 15-year-old girl last year.
He stepped down from his congressional seat in 2011 over a series of sex scandals and was again exposed during his 2013 bid for New York City mayor.
He may have to register as a sex offender and could face prison time.
Mr Weiner is expected to enter his plea at a Manhattan court on Friday morning, according to local media.
He again made headlines during last year’s US presidential election.
During an investigation into the sexting allegation, FBI officials found emails on Mr Weiner’s laptop from his ex-wife, Huma Abedin, who was a top aide to Democratic candidate Hillary Clinton.
An FBI investigation into Mrs Clinton’s private use of email while she was secretary of state was closed after officials said nothing incriminating was found.
The FBI began investigating Mr Weiner last September after the Daily Mail reported that he exchanged lewd messages with a teen from North Carolina for several months.
The newspaper, which did not identify the girl, suggested that Mr Weiner knew she was under age at the time.
The girl also accused him of asking her to undress on camera.
A month earlier, Ms Abedin announced she was separating from her husband after a report emerged that he allegedly sent a photo of himself in his underpants with his toddler son nearby.
The New York Post reported that Mr Weiner sent sexual messages along with the alleged photo to an unidentified woman in 2015.
Once a rising Democratic star, Mr Weiner stepped down from Congress in June 2011 after a graphic image sent from his Twitter account went public.
Initially claiming his account was hacked, he eventually confessed to having lied.
He also admitted indulging in explicit online exchanges with at least six other women and pledged to seek therapy.
Mr Weiner attempted to revive his political career in 2013 by running for mayor of New York.
But his campaign imploded amid reports of further graphic online messages.
Ex-congressman Anthony Weiner expected to admit sexting