Russia has committed to helping military governments in Mali, Burkina Faso and Niger acquire arms and training for a planned 5,000-strong force to deploy in the central Sahel region, a statement said.
The West African nations, run by juntas that have taken power in coups in recent years, have formed a body known as the Alliance of Sahel States.
The grouping has kicked out French and other Western forces and turned towards Russia, mainly fighters from the Wagner mercenary outfit, for military support. It has also withdrawn from West Africa's main political and economic bloc ECOWAS.
The foreign ministers of the three West African countries travelled to Moscow for meetings beginning on Thursday with Russian Foreign Minister Sergei Lavrov.
Russia voiced "unwavering support" for the joint force announced in January, a joint alliance and Russian statement said.
The ministers agreed to facilitate acquisition of "major and high-performance military equipment and appropriate training" for the force and Russia is ready "to provide the necessary technical assistance", it said.
The statement did not offer details.
The three countries' armies are fighting a jihadist insurgency that has spread across the region south of the Sahara since it first took root in Mali in 2012.
The largely rural insurgency has killed thousands of civilians and displaced millions.
Writing by Robbie Corey-Boulet