The government had indicated the privatization of up to 40 percent of the group would take place next year as part of a drive aimed at helping pay down its debt, which stands at €2.2 trillion.
Italy's postal service was successfully listed in October in the first of a series set to include the privatization of air traffic controller Enav.
But Ferrovia dello Stato CEO Renato Mazzoncini, who took up his post on Tuesday, said the railway would only be listed "when we're ready", insisting rushing the sale would be folly because "the stock market does not forgive".
The group recorded a net profit of €292 million ($317 million) in the first half of 2015, up 2.5 percent from the same period last year, with an operating profit of some €948 million, up 0.7 percent.
The company, which marked a €8.4 billion turnover last year, employs more than 69,000 people.
Supporters say the privatization will improve Italy's slow and shabby regional rail services, which lag far behind its sleek and more lucrative high-speed railways.