IPG said it would redistribute these holdings among the four remaining operating groups after AMS is dissolved.
In the filing, IPG stated it is likely to scrap AMS after its widely anticipated sale of marketing research firm NFO WorldGroup, one of AMS's main components.
IPG has put NFO on the market in a bid to generate some cash to reduce its debt.
The dissolution of AMS also raises questions about Weber Shandwick founder Larry Weber's future, who has been chairman and CEO of AMS.
A Weber spokeswoman said he is expected to remain involved in IPG, and Weber Shandwick in particular. IPG was unavailable for comment.