Kigali had expected to assume the chairmanship of the 11-member bloc at a meeting on Saturday in Equatorial Guinea.

Instead, the bloc kept Equatorial Guinea in the role, which Rwanda’s foreign ministry denounced as a violation of its rights.

Rwanda, in a statement, condemned Congo’s “instrumentalization” of the bloc and saw “no justification for remaining in an organization whose current functioning runs counter to its founding principles.”

It wasn’t clear if Rwanda’s exit from the bloc would take immediate effect.

The office of Congolese President Felix Tshisekedi said in a statement that ECCAS members had “acknowledged the aggression against the Democratic Republic of Congo by Rwanda and ordered the aggressor country to withdraw its troops from Congolese soil.”

M23 seized eastern Congo’s two largest cities earlier this year, with the advance leaving thousands dead and raising concerns of an all-out regional war.

African leaders along with Washington and Doha have been trying to broker a peace deal. Congo, the U.N. and Western powers accuse Rwanda of supporting M23 by sending troops and weapons.

Rwanda has long denied helping M23, saying its forces were acting in self-defence against Congo’s army and ethnic Hutu militiamen linked to the 1994 Rwandan genocide that killed around 1 million people, mostly ethnic Tutsis.

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U.S. President Donald Trump’s administration hopes to strike a peace accord between Congo and Rwanda that would also facilitate billions in Western investment in the region, which is rich in minerals including tantalum, gold, cobalt, copper and lithium.

ECCAS was established in the 1980s to foster cooperation in areas like security and economic affairs among its member states.