Fox may join in a $100-million film offering.

According to a preliminary prospectus, Shearson Lehman Bros. would sell publicly offered units for a minimum of $25 million and a maximum of $100 million by Sept. 15 to fund a new limited partnership, American Entertainment Partners. The partnership, in turn, would form a joint venture with 20th Century Fox Film to produce or acquire interests in about 15 to 20 films. The partnership is not intended to generate tax shelter benefits, according to the preliminary document.