Nielsen equivalence in Gupta-Sidki groups

For a group $G$ generated by $k$ elements, the Nielsen equivalence classes are defined as orbits of the action of $\mathrm{Aut}{F}_k$, the automorphism group of the free group of rank $k$, on the set of generating $k$-tuples of $G$. Let $p\ge 3$ be prime and $G_p$ the Gupta-Sidki $p$-group. We prove that there are infinitely many Nielsen equivalence classes on generating pairs of $G_p$.