  Contributions from gluon interactions, which are non-leading in high-energy
semi-hard processes, are studied and represented in terms of reggeon exchanges.
Unlike the leading gluonic reggeon, related to the BFKL pomeron, the
non-leading reggeons are sensitive to the spin and transverse momentum
distributions of scattering partons. There are several gluonic reggeons with
poles in the vicinity of angular momentum $j=0$ contributing to the
perturbative Regge asymptotics of QCD. We extend the high-energy effective
action including sub-leading terms which describe these reggeons and their
interactions with scattering quarks and gluons in the multi-Regge
approximation.
