  We have calculated all the components of the current in a short
one-dimensional channel between two superconductors for arbitrary voltages and
transparencies $D$ of the channel. We demonstrate that in the ballistic limit
($D\simeq 1$), the crossover between the quasistationary evolution of the
Josephson phase difference $\varphi$ at small voltages and transport by
multiple Andreev reflections at larger voltages can be described as the
Landau-Zener transition induced by finite reflection in the channel. For
perfect transmission and vanishing energy relaxation rate the stationary
current-phase relation is never recovered, and $I(\varphi)=I_c \mid \sin
\varphi /2 \mid \mbox{sign} V$ for arbitrary small voltages.
