Gabon’s debt-for-nature swap is edging closer to reality as the African nation tests international markets with a $500 million bond deal.

The notes, which are being sold by the Gabon Blue Bond Trust and marketed by Bank of America, are expected to price as soon as Wednesday, according to people familiar with the matter, who asked not to be named because the matter is private.

The new debt will be used to help fund a buyback of existing sovereign debt and finance environmental protection efforts.