  The general procedure of constructing a consistent covariant Dirac-type
bracket for models with mixed first and second class constraints is presented.
The proposed scheme essentially relies upon explicit separation of the initial
constraints into infinitely reducible first and second class ones (by making
use of some appropriately constructed covariant projectors). Reducibility of
the second class constraints involved manifests itself in weakening some
properties of the bracket as compared to the standard Dirac one. In particular,
a commutation of any quantity with the second class constraints and the Jacobi
identity take place on the second class constraints surface only. The developed
procedure is realized for N=1 Brink--Schwarz superparticle in arbitrary
dimension and for N=1, D=9 massive superparticle with Wess--Zumino term. A
possibility to apply the bracket for quantizing the superparticles within the
framework of the recent unified algebra approach by Batalin and Tyutin [20--22]
is examined. In particular, it is shown that for D=9 massive superparticle it
is impossible to construct Dirac-type bracket possessing (strong) Jacobi
identity in a full phase space.
