  A variety of three-dimensional left-covariant differential calculi on the
quantum group $SU_q(2)$ is considered using an approach based on global $ U(1)
$ -covariance. Explicit representations of possible $q $-Lie algebras are
constructed in terms of differential operators. A gauge covariant differential
algebra is uniquely determined. The non-standard Leibnitz rule is obtained for
a corresponding $q$-Lie algebra.
