  A left-invariant sub-Riemannian metric $d$ on the shortened Lorentz group
$SO_0(2,1)$ under the condition that $d$ is right-invariant relative to the
orthogonal Lie subgroup $1\otimes SO(2)$ is studied. The distance between
arbitrary two elements, the cut locus (as the union of the subgroup $1\otimes
SO(2)$ with the antipodal set to the submanifold of symmetric matrices in the
open solid torus $SO_0(2,1)$), and the conjugate set for the unit are found for
$(SO_0(2,1),d)$.
