Pope Francis called on the world's Catholic cardinals, many of whom live in Rome and lead Vatican offices, to pursue a "zero deficit" agenda to improve the Vatican's use of its economic assets.

The pontiff did not offer many specifics in a letter published by the Vatican on Friday, but he said the budget agenda would require "a further effort" by the 236 cardinals, the highest officials in the 1.4 billion-member Roman Catholic Church.

Francis, pope since March 2013, has pursued a series of Vatican financial reforms but has also been beset by several scandals, including a Vatican investment in a London property that resulted in a loss of some 140 million euros ($156 million).

One of the financiers of that deal took the Vatican to trial at London's High Court this summer over alleged damage to his reputation. A verdict is expected later this year.

Francis' letter, addressed to his "venerable brothers" and signed Sept. 16, did not say whether the pope had specific budget cuts in mind.

The pontiff said he was looking for "implementation of ethical policies that allow for improving the economic performance of existing assets".

"On the cost reduction side, we need to give a concrete example so that our service is carried out with a spirit of essentiality, avoiding the superfluous and selecting our priorities well," the pope wrote.

The headquarters of the Catholic Church comprises two entities, the internationally recognised sovereign entity of the Holy See and Vatican City, a 108-acre city-state surrounded by Rome.

They maintain separate budgets, and Vatican City income, including from the popular Vatican Museums, has often been used to plug deficits in the Holy See's budget.

In July, Vatican City's central bank reported a surplus of 45.9 million euros ($51 million) for its financial and real estate holdings over the course of 2023.