VATICAN CITY (Reuters) - 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.

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

"We are all fully aware now that urgent structural measures, which can no longer be postponed, are needed to achieve sustainability of the pension fund."

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.