Marchionne conceded that an IPO of Chrysler could delay his plans to fully merge Fiat with Chrysler.
A Chrysler IPO would be technically ready by the end of the year, Marchionne added, but that the markets would probably be better positioned in the first quarter of next year. The SEC filing will be ready by the end of the month, he said.
Marchionne has said he favors buying the trust's stake outright over selling shares in Chrysler to the public in order for the trust to make money from its stake. That would allow him eventually to list a cominbed Fiat-Chrysler.
The two sides are at stalemate despite a July ruling from a Delaware judge siding with Fiat over the formula for setting the price for a 3.3-percent tranche of Chrysler shares. The judge declined to issue a final ruling, saying he wanted to hear more evidence.
The court's ruling, if a settlement isn't reached first, would be a benchmark for the pricing of 16.6 percent of the minority shareholder's stake. The remaining would be up for negotiation.
Fiat already has already exercised three call options of 3.3 percent each, and has options on two more in January and July 2014.
Marchionne skipped the Frankfurt auto show this week, fueling speculation about the status of negotiations for the Chrysler stake. Marchionne cited "work commitments," without elaborating.