  The nonperturbative equation for the infrared $\Pi_{44}(0)$-limit is built by
using the Slavnov-Taylor identity to define the three-gluon vertex function in
the temporal axial gauge. We found that all vertex corrections should be taken
into account along with the standard ring graphs to keep the gauge covariance
throughout calculations and to give correctly the nonperturbative $g^3$-term.
This term is explicitly calculated and compared with the previously known
results.
