* Chrysler IPO documents to be filed this month - Marchionne * Minority shareholder VEBA would sell some shares in IPO * Follows deadlock in talks for Fiat to buy VEBA's stake By Francesca Landini and Deepa Seetharaman MILAN/DETROIT, Sept 16 (Reuters) - Chrysler Group LLC plans to file documents this month that would allow its minority investor to sell shares in a stock market listing, a process that will slow Italian carmaker's Fiat SpA's plans to take full control of the U.S. automaker. An initial public offering would bring to a head the ongoing battle between Sergio Marchionne, who has led both companies since Chrysler's government-financed bankruptcy in 2009, and a healthcare trust fund affiliated with the United Auto Workers union. The trust, a type known as a voluntary employees' beneficiary association or VEBA, is unhappy with the price Fiat has offered for its Chrysler stake.