Pope Francis is warning that the Vatican's troubled pension fund faces a “serious imbalance” and cannot guarantee future obligations without “urgent structural” reforms.

Pope Francis said on Thursday the Vatican's pension fund is facing a "serious imbalance" that may require changes to its operating structure, and appointed a senior cardinal to take over the fund's administration.

In a Nov. 21 letter to cardinals, prefects, and managers in the Roman Curia, the pope underlined the gravity of the unsustainability of the pension fund.

Pope Francis, who has imposed a series of cost-cutting measures across the cash-strapped Vatican, warned Thursday that the city state's troubled pension fund needs urgent reform to guarantee future obligations.