Pope Francis has broken with Catholic tradition to appoint a woman as an undersecretary of the synod of bishops, the first to hold the post with voting rights in a body that studies major questions of doctrine.

Frenchwoman Nathalie Becquart is one of the two new undersecretaries named Saturday to the synod, where she has been a consultant since 2019.

The appointment signals the pontiff's desire "for a greater participation of women in the process of discernment and decision-making in the church", said Cardinal Mario Grech, the secretary-general of the synod.

"During the previous synods, the number of women participating as experts and listeners has increased," he said.

"With the nomination of Sister Nathalie Becquart and her possibility of participating in voting, a door has opened."

The synod is led by bishops and cardinals who have voting rights and also comprises experts who cannot vote, with the next gathering scheduled for autumn 2022.

A special synod on the Amazon in 2019 saw 35 female "auditors" invited to the assembly, but none could vote.

The Argentinian-born pope has signalled his wish to reform the synod and have women and laypeople play a greater role in the church.

He named Spaniard Luis Marin de San Martin as the other under undersecretary in the synod of bishops.

Becquart, 52, a member of the France-based Xaviere Sisters, has a master's degree in management from the prestigious HEC business school in Paris and studied in Boston before joining the order.