Mali, Burkina Faso and Niger have announced a new 0.5% levy on imported goods in their bid to fund a new three-state union after leaving the larger regional economic bloc.
The Alliance of Sahel States began in 2023 as a security pact between the military rulers of the three West African countries, who took power in coups in recent years.
It has since grown into an aspiring economic union with plans for biometric passports and closer economic and military ties.
A statement by the Bloc says the levy which has taken effect, will affect all goods imported from outside the three countries, but will not include humanitarian aid.
The move ends free trade across West Africa, states of which have for decades fallen under the umbrella of the Economic Community of West African States (Ecowas), and highlights the rift between the three states that border the Sahara Desert and influential democracies such as Nigeria and Ghana to the south.
Ecowas had imposed economic, political and financial sanctions on the three in a bid to force them to return to constitutional order, to little effect.
Mali, Burkina Faso and Niger are some of the poorest countries in the world and have been overrun by an armed Islamist insurgency over the past decade.
