  We first introduce the class of bipartite absolute retracts with respect to
tree obstructions with at most $k$ leaves. Then, using the theory of
homomorphism duality, we show that this class of absolute retracts coincides
exactly with the bipartite graphs which admit a $(k+1)$-ary near-unanimity (NU)
polymorphism. This result mirrors the case for reflexive graphs and generalizes
a known result for bipartite graphs admitting a $3$-NU polymorphism.
