  The odderon singularity is studied in perturbative QCD in the framework of
the Bartels-Kwieci\'nski-Praszalowicz (BKP) equation. Arguments for the odderon
intercept being exactly equal to unity are given. Besides, a variational method
based on a complete system of one-gluon functions is presented. For the
odderon, the highest intercept calculated by this method is
$1-(N_c\alpha_{s}/\pi) 0.45$. Comparison to other calculations is shown.
