  We propose how to explicitly introduce the Jaffe-Witten mass gap into the
quantum Yang-Mills theory. Through the full gluon propagator it is defined as
such nonperturbative scale that when it formally goes to zero, then the
perturbative phase survives in the theory only. The close link between mass gap
and strong infrared singularities which are due to dominated in the QCD vacuum
self-interaction of massless gluons is also discussed. This interaction leads
thus to the zero momentum modes enhancement effect in the QCD nonperturbative
vacuum. Using theory of distributions, we argue that strong nonperturbative
infrared singularities can be put under control. A new, intrinsically
nonperturbative phase in QCD is established.
