Hard-soft factorization in B_c--> psi pi decay

The width of $B_c^+\to \psi \pi^+$ decay is calculated in the framework of factorization of a hard gluon exchange and a soft binding of quarks in the heavy quarkonium, so that ${\rm BR}(B_c^+\to \psi \pi^+) = 2.0\pm 0.5$ \%.