  Planar superconducting junctions with a large effective Josephson coupling
constant and a pronounced interface pair breaking are shown to represent weak
links with small critical currents and strongly anharmonic current-phase
relations. The supercurrent near Tc is described taking into account the
interface pair breaking as well as the current depairing and the Josephson
coupling-induced pair breaking of arbitrary strengths. A new analytical
expression for the anharmonic supercurrent, which is in excellent agreement
with the numerical data presented, is obtained. In junctions with a large
effective Josephson coupling constant and a pronounced interface pair breaking,
the current-induced depairing is substantially enhanced in the vicinity of the
interface thus having a crucial influence on the current-phase relation despite
a small depairing in the bulk.
