  The action functional for a linear elastic medium with dislocations is given.
The equations of motion following from this action reproduce the
Peach-K\"{o}hler and Lorentzian forces experienced by dislocations. The
explicit expressions for singular and finite parts of the self-force acting on
a curved dislocation are derived in the framework of linear theory of
elasticity of an isotropic medium. The velocity of dislocation is assumed to be
arbitrary but less than the shear wave velocity. The slow speed and near-sonic
motions of a dislocation are investigated. In the near-sonic limit, the
explicit expression for the leading contribution to the self-force is obtained.
In the case of slowly moving dislocations, the effective equations of motion
derived in the present paper reproduce the known results.
