The present disclosure relates to RNA amidates and thioamidates useful for RNA interference applications. The RNA amidates and thioamidates contain at least one internucleoside linkage chosen from ribo-N3'.fwdarw.P5' phosphoramidate (NP) and ribo-N3'.fwdarw.P5' thiophosphoramidate (NPS) linkages, and optionally further containing at least one covalently conjugated lipid moiety. Compositions comprising the amidates and thioamidates are disclosed, as are methods for their use in modulating gene expression.