(Reuters) -The U.S. Department of Justice could file an antitrust lawsuit against concert promoter Live Nation Entertainment and its unit Ticketmaster by the end of the year, Politico reported on Friday, citing three people with knowledge of the matter.

Shares of Live Nation dropped 5% in extended trading on Friday.

Earlier this year, U.S. senators slammed Live Nation's lack of transparency and inability to block bot purchases of tickets following a major fiasco involving ticket sales for Taylor Swift's long-awaited concert tour.

The potential lawsuit could claim that the entertainment giant is abusing its power over the live music industry, Politico reported, adding that the timing of the case was not firm and the DOJ could decide to drop it.

Live Nation and the DOJ did not immediately respond to Reuters requests for comment.

(Reporting by Urvi Dugar and Yuvraj Malik in Bengaluru; Editing by Devika Syamnath)