Following a "poison pill" strategy to thwart activist investors, Fitch Ratings lowered its ratings of Navistar International Corp. and put it on watch for future downgrades, BloombergBusinessweek reports.  Fitch said recent changes introduce some uncertainty about the company's long-term operating and financial policies.  

Meanwhile, CNBC reported rumors that Volkswagon and Fiat had expressed interest in purchasing the company 

Gimme Credit analyst Vicki Bryan sees a possible end for Navistar.

"Given Navistar's spectacularly bad press over the past few weeks ... we can envision a scenario similar to the coup d'état at Texas Industries in 2009," Byran said, "when its largest shareholders launched a public grass root appeal to all shareholders to support their new board candidates as well as sweeping changes to improve management strategy and company disclosures."

Bryan also pointed out that even if Navistar can survive its troubles with activist investors, the company's fate still hinges on its ability to produce a new type of truck engine that meets EPA emissions guidelines.

Navistar hasn't yet addressed the possibility of bankruptcy, however, one spokeswoman told CNBC, "it's important to the future of the company to either get a final ruling in place by the courts (presumably in its favor)" or EPA certification "in a timely manner." 

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