The company, whose shares fell 8.5 percent in premarket trading, was expected to report financial results for the fourth quarter and full year ended December 31 later on Thursday. It said it now expected to file its annual report by March 15 and will reschedule its fourth-quarter and full-year 2012 earnings conference call to coincide with this filing.

Molycorp, which last month warned of significantly lower-than-estimated revenue and cash flow for the first half of this year, said it expected the goodwill impairment charge to be "substantial."

(Reporting by Euan Rocha; Editing by Lisa Von Ahn)