Radio giant iHeartMedia Inc. is circulating documents for a bankruptcy filing that could come as soon as this weekend.

Despite a year of negotiations on a restructuring plan, a formal support agreement still isn't in place with the most-senior lenders, making a bankruptcy filing all but certain, Bloomberg News reported on Thursday.

With 855 stations, iHeartMedia, once known as Clear Channel Communications, is the largest radio station group owner in the United States.

It has 18 stations in Massachusetts, including 10 in Boston (Kiss 108, Jam'n 95.5, Evolution 101.7, Rumba 1430, Talk 1200, 101.7 The Bull, 100.7 WZLX, New 97.7, WBZ 1030 and WRKO 68); three in Cape Cod (95 WXTK, 106 WCOD and Cool 102), three in Springfield (Mix 93.1, Kix 100.9 and WHYN NewsRadio 560); and two in Worcester (96.1RSR and WTAG News Radio 580 / 94.9).

Traditional radio is facing a bleak future, according to an August 2017 study by New York University's Steinhart Music Business Program. Teh study found it has failed to engage listeners born after 1995 and its influence and relevance is waning fast.

AM/FM radio is in the midst of a massive drop-off as a music-discovery tool by younger generations, with self-reported listening to AM/FM radio among teens aged 13 and up declining by almost 50 percentage points between 2005 and 2016, the report stated. Music discovery as a whole is moving away from AM/FM radio and toward YouTube, Spotify and Pandora.

Since 2008, iHeartMedia, Inc., has struggled to pay down more than $20 billion in debt the company acquired from its leveraged buyout.

Last April, the San Antonio-based iHeartMedia warned investors it might not survive the next 10 months.

Liberty Media, the parent company of satellite radio's SiriusXM, has shown an interest in piping in $1.16 billion and acquiring a 40 percent stake in iHeartMedia, Forbes reported.