Moody’s, a global finance and ratings agency, says it would be detrimental if the three nations also decided to leave the West African Economic and Monetary Union, WAEMU, though that was not expected.
The three military junta-led countries announced on Sunday that they were planning to leave ECOWAS, the region's main economic and political bloc.
"The three countries' departures would disrupt the economic integration that is ECOWAS' raison d'etre and weigh on business confidence, potentially hindering the bloc's economic growth," said Moody's in a statement.
"While not our baseline expectation, an exit from WAEMU would be much more detrimental to sovereigns leaving the monetary union because of the credit support that WAEMU membership provides in terms of macroeconomic stability and reduced external vulnerability," it added.
Burkina Faso’s Prime Minister Appolinaire Joachimson Kyelem de Tambela spoke on the ECOWAS exit after a cabinet council late on Tuesday.
The decision to leave the regional body was a “carefully considered decision” in response to hopes for “total sovereignty,” he said, adding that it was “preceded by an indepth analysis of the functioning of the institution and of the possible consequences of the withdrawal."
Tambela also noted that there will be economic consequences on Burkina Faso, Niger and Mali.
But he said they were convinced of being able to "create a viable, resilient economic space that is listening to the true aspirations of our populations."
Grappling with jihadist violence and poverty, Burkina Faso, Niger and Mali set up a mutual defense pact, the Alliance of Sahel States, AES in September.
All three say they have formally notified ECOWAS of their withdrawal. Tambela said ECOWAS had been transformed into a "technocratic instrument" and criticized its "indifference" to the countries' problems.
ECOWAS has said it wants "a negotiated solution to the political impasse" with all three nations.
Information for this article was sourced from Reuters and Agence France-Presse.